Seasickness

Seasickness is a common and significant medical illness for mariners at sea, often responsible for maritime rescue operations. During stormy weather, mariners frequently consider seasickness a medical emergency and justification for medical evacuation. Each year, seaworthy yachts are abandoned because their exhausted and despondent crews have lost the collective will to persevere. “They are wet, seasick, scared, and want to go home,” observed a merchant marine captain (personal communication with author).

Seasickness is a self-limited condition; symptoms subside as one acclimates over 2 to 3 days. The balance center’s ability to adapt to new sea conditions is commonly called “getting your sea legs.” Nearly everyone will develop seasickness with sufficient stimuli; however, individual susceptibility is enormously variable. Pregnant women are highly susceptible, especially in the first trimester.

At best, seasickness (mal de mer) is moderately disabling. It can lead to rapid mental and physical deterioration marked by progressive dehydration, loss of manual dexterity, ataxia, loss of judgment, and loss of the will to survive. Fatalities from seasickness have occurred because of poor seamanship and complications arising during hazardous emergency evacuations.

Seasickness impairs cognitive function. Sailors often lose the ability to multitask, making it difficult to analyze and integrate complex data, which leads to impaired judgment and faulty decisions. Cognitive failure is also expressed as loss of short-term memory. This impairment makes it difficult to engage in problem solving. Compounding this problem are the medications used to prevent or treat seasickness. Their side effects may include drowsiness, confusion, and loss of concentration. The underlying mechanism of seasickness involves a conflict of sensory input processed by the brain to orient the body’s position. Someone positioned in the cabin of a heeling or rolling boat is inviting seasickness. Below decks, the eyes oriented to the cabin sole and ceiling detect no tilt from vertical, while fluid in the inner ear’s vestibular system (semicircular canals and the otolith organs) constantly shifts. Position sensors (proprioceptors) in the neck, muscles, and joints send additional signals, depending on how a person shifts and secures him or herself from falling. This mix of sensory data from the eyes, inner ear, and position sensors arrives in complex and conflicting combinations, creating a “sensory conflict” that activates the emetic center in the brainstem. According to Dr. Charles Omen, Director of the Man Vehicle Space Lab at MIT and an authority on motion sickness, sensory conflict is a sensory cue “expectancy” conflict, not an intermodality conflict. It occurs when signals from the inner ear don’t match expectations based on one’s own commanded self movement, or concurrent visual or proprioceptive cues. In response to this “sensory conflict,” there is activation of a complex and not well-understood anatomic connection between the vestibular nuclei in the brainstem, the cerebellum, and the autonomic and emetic centers. Stimuli from the vestibular and visual systems can independently initiate symptoms. Sickness occurs most commonly with acceleration in a direction perpendicular to the longitudinal axis of the body, which is why head movements away from the direction of motion are so provocative. When these stimuli are presented in isolation in the laboratory, visual stimulation is more important than vestibular input in causing motion sickness. There is no increase in symptoms when combined stimulation is applied. Blind people can become seasick; the conflict arises when input from the vestibular system does not match the individual’s expectations derived from previous motion experience. The intensity of conflicting input can be amplified when compared with these expectations. Deaf subjects are susceptible to motion sickness. If the semicircular canals and otolith organs produce sensory cues that are incongruous, seasickness ensues. If the visual system indicates movement but the vestibular system does not (in-flight simulators and movie theaters), motion sickness may ensue. Medication is more effective in preventing symptoms than in reversing them. Therefore, anti-seasickness medication should be administered before leaving port, or the night prior to departure (Table 83-1). One should begin any trip well hydrated and free of the after-effects of alcohol, which impairs vestibular function by sensitizing the vestibular apparatus to motion. One is advised to eat lightly. Anecdotal reports favor eating carbohydrates rather than protein, but no conclusive study favors any particular food or diet. Many sailors favor eating soda crackers or bread. One should try to snack on bland foods throughout the day, even if anorectic, to maintain energy levels until meals are regularly tolerated. Cheese and crackers, energy bars, fruit, trail mix, dry granola, and popcorn work best. Drinking small amounts of fluid frequently is recommended to avoid dehydration. Many sailors believe drinks high in vitamin C prevent seasickness; however, there are no data to support this notion.

TABLE 83-1 Medications for Seasickness

Ginger is often recommended as an antiemetic and may be clinically useful in individual cases. However, there are very few controlled trials. In one trial, ginger was tested in a double blind, randomized, placebo-controlled study of 80 naval cadets in rough seas. Seasick cadets were given a gram of ginger or placebo hourly for 4 hours. Ginger significantly reduced vomiting and cold sweats, and minimally decreased nausea and dizziness. Ginger is readily available in 500-mg capsules in health food stores and sold in marine stores as Sailor’s Secret. The suggested dose is 1000 mg every 6 hours, starting one-half hour prior to the trip; it is less effective when given to someone who is already nauseated. The capsules can be supplemented with foods containing lower concentrations of ginger, such as gingersnap cookies, ginger ale or tea, and candied ginger. Too much ginger may cause heartburn; people with gallstones should not take it, because it can provoke an attack of biliary colic by stimulating the flow of bile.

Both field and laboratory experiments have documented the efficacy of acupressure in preventing seasickness. However, some experts on space and motion sickness still consider acupressure no better than a placebo. One sea trial showed that acustimulation suppressed the symptoms of motion sickness. Pressure should be applied on the Neiguan P6 point of the forearm over the median nerve. This is found two to three fingerbreadths proximal to the wrist joint between the two prominent finger flexor tendons. There are commercially available elastic wrist straps with plastic studs that create pressure over the P6 point. A wristwatch-like device is sold to deliver transcutaneous electrical stimulation to the median nerve; these have not been proved useful for seasickness, but have many advocates.

Recommendations for preventing seasickness are directed toward reducing sensory conflict by limiting the time below decks while underway. This will help the eyes to see what the “the ears are feeling.” After departure, stay on deck and amidships (center) or aft (toward the stern), where pitching and rolling are less severe. Obtain a broad view of the horizon using direct and peripheral vision. This provides a stable and level point of reference. Avoid close visual tasks such as prolonged reading, writing, and navigation. Avoid areas with fumes (especially diesel) and odors that can stimulate nausea. Continue medication for preventing seasickness at the suggested intervals; try tapering the dose after the first or second day.

The early signs and symptoms of seasickness are yawning, sighing, dry mouth or salivating, drowsiness, headache, dizziness, and lethargy. With sustained exposure to the stimulus, gastric emptying is inhibited. Pallor, cold sweats, belching, nausea, dry heaves, and vomiting ensue. Some persons don’t have gastrointestinal complaints but experience headache, apathy, and depression. The side effects of some anti-seasickness medications mimic seasickness, creating a diagnostic dilemma. The window of opportunity for early intervention is often missed because early signs are not recognized or the victim is in denial.

At the first sign of seasickness, one immediate remedy for many is to take the helm and steer. The active mental and physical activity to steer the ship, together with the visual focus on the horizon and waves, presumably creates neural feedback loops that help to reorient the body’s equilibrium. One should stand and feel the waves, and steer the boat by reference to clouds, the horizon, distant marks and oncoming waves, posturing to anticipate the boat’s motion by “riding” the waves. Wave riding synchronizes sensory input and expectations of motion. As best possible, one should keep the head, shoulders and upper body balanced over the hips, to stay in balance and gain postural control gracefully, as though the body was truly “gimbaled” on the deck. Sitting in the cockpit, one can still ride the waves and watch the horizon. Chuck Omen developed the concept of wave riding. He advises: “Don’t sit or lie inert in the cockpit, passively letting the motion toss you around. Postural anticipation of the boat’s motion is the natural cure for seasickness.” Debilitated seasick persons can easily fall or be washed overboard. They should always wear a safety harness on deck and be closely monitored. In storm conditions, the safest place to be secured is below in a bunk.

If symptoms progress, one may lie down in a secure, well-ventilated bunk, face up with eyes closed and head still in an attempt to sleep. Parenteral antinausea medications include the phenothiazine derivative promethazine hydrochloride (Phenergan). This drug has powerful antidopaminergic, anticholinergic, and antihistamine properties. The latter effects predominate (see other side effects below). Anticholinergic side effects include constipation, xerostomia, blurred vision, and urinary retention. Phenergan should be used with caution in persons with decreased gastrointestinal motility, gastrointestinal obstructions (partial or complete), urinary retention, urinary obstruction (partial or complete), benign prostatic hypertrophy, xerostomia, or visual problems. Rare but serious adverse effects of promethazine include extrapyramidal reactions.

Promethazine is useful for prophylactic and active treatment of seasickness and can be administered as a suppository, by deep IM injection, and orally as a tablet or syrup. NASA astronauts use a combination of intramuscular or oral promethazine with oral dexedrine (to counter the drowsiness induced by promethazine). Some sailors prefer prochlorperazine suppositories for nausea, and many have used ondansetron (Zofran) oral disintegrating tablets to treat nausea and vomiting. Ondansetron does not, however, prevent seasickness.

Transdermal scopolamine hydrobromide (Transderm Scōp patch) is the most popular anticholinergic agent used for prevention of motion sickness. Scopolamine prevents motion-induced nausea by inhibiting vestibular input to the central nervous system, resulting in inhibition of the vomiting reflex. It may also act directly on the vomiting center. The drug is delivered via an adhesive patch placed behind the ear 4 or more hours before departure; the patch will last for up to 3 days, often with minimal side effects. The most common adverse effects are dry mouth (66%) and drowsiness (17%). Other undesirable side effects include blurred vision (which may persist for weeks), dry mucous membranes, short-term memory loss, and problems denoted by the well-known mnemonic “hot as hell, dry as a bone, blind as a bat, mad as a hatter.” To reduce the dose of scopolamine, allow only one-half of the intact patch to contact the skin by placing the other one-half onto a Band-Aid or tape attached to the area. Do not disrupt the integrity of the disc by cutting it. Follow the directions carefully, and wash hands thoroughly after application because temporary blurring of vision and dilation of the pupils may occur if the drug is on your hands and comes in contact with the eyes. Apply only one disc at a time. Scopolamine is contraindicated for children, persons with narrow-angle glaucoma (remove the patch immediately if eye pain occurs suddenly), and men with prostatic hypertrophy. Long-term use may produce withdrawal symptoms such as nausea, dizziness, headache, and equilibrium disturbances. Scopolamine in pill form (Scopace) is an alternative to the patch. The chief advantage is the dosing flexibility. The fixed dose from the patch may be excessive for small individuals and inadequate for larger people. Taking the lowest effective dose can minimize side effects. The current recommendation is one tablet (0.4 mg) or two (0.8 mg) 1 hour prior to departure, and one to two tablets every 8 hours as needed thereafter.

The antihistamines meclizine (Bonine) and dimenhydrinate (Dramamine) are available over the counter (OTC) without prescription. They are effective for many sailors, as are the other prescription medications listed in Table 83-1. The popular antihistamine cinnarizine (Stugeron) is not sold in the United States, but is available OTC in Europe, Bermuda, Mexico, and Canada. It can be obtained legally from http://www.canadadrugsonline.com. It is favored by many sailors because it is less sedating than all the other antihistamines and has fewer reported side effects (described below).

Side effects of over-the-counter antihistamines include drowsiness, dry mouth, blurred vision, irritability, urinary retention, dizziness, and headache. Meclizine (Bonine) is thought to cause less drowsiness and confusion. Antihistamines cause thickened bronchial secretions, and should be used with caution in people with asthma and chronic obstructive pulmonary disease. An effective nonprescription drug for drowsiness is the decongestant pseudoephedrine, which is available in doses of 30 to 100 mg; caffeine 200 mg is also useful and may potentiate the beneficial effects of promethazine. The newer generation of nonsedating antihistamines is ineffective in preventing seasickness.

All therapies are subject to placebo effect, and there are no well-controlled trials comparing and evaluating different treatments. Many products cite only testimonials. The protection conferred by drugs is a matter of degree; there is no magic bullet to prevent seasickness in everyone. It is not uncommon for one drug in a category (e.g., antihistamine) to be effective and a related drug to provide no benefit; the same is true for side effects. Evaluate medication side effects before boating. If all else fails, follow Samuel Johnson’s 18th-century advice: “To cure seasickness, find a good big oak tree and wrap your arms around it.”

Health Maintenance at Sea

The “Fearsome Five” are health issues that must be addressed to maintain optimal physical and mental performance: food (calorie depletion), fluid (dehydration), Fahrenheit (hypothermia), fatigue (sleep deprivation), and fitness (injury, illness, infection).

Life Jackets

Annual Coast Guard recreational boating fatality statistics underscore the need for boaters to wear life jackets. In 2010, for example, 484 (72%) of 672 recreational boating fatalities were due to drowning. The vast majority of these cases involved boats under 8 m (26 feet), including open motorboats, personal water craft, canoes, and kayaks. Each annual report estimates that at least 85% to 90% of these drowning deaths could have been prevented if a life jacket had been worn. Life jackets help prevent drowning in water at any temperature, but they are vital to simply combat the lethal effects of cold water. Few boaters routinely wear life jackets, and most people put them on only in storm conditions. The main reasons for veteran sailors not wearing life jackets are discomfort and inconvenience. All the conventional (foam or kapok-filled) type I offshore life jackets and type II near-shore life vests are bulky, uncomfortable, and awkward to wear; they are too warm in summer, and limit mobility. The common type III vest is comfortable and wearable, but has poor reserve buoyancy and freeboard (distance from the water to the mouth); it cannot turn the unconscious victim face up (righting ability) and cannot support the head (maintain an airway). It is suitable only for calm water and should be worn only by active boaters who are able to swim, or in situations where the chance of a quick rescue is assured. Life jackets should be selected according to comfort and practicality in order to maximize compliance. Nonswimmers, children, and inexperienced crew should wear life jackets at all times whenever on deck or in an open boat. Everyone on deck should wear a life jacket in heavy weather, at night, when visibility is reduced, when the boat is traveling quickly, or traversing cold waters. In warm waters, experienced boaters who are strong swimmers must acknowledge a degree of risk by not wearing flotation.

Inflatable vests have a flat and lightweight design that allows them to lie flush against the body so they do not restrict movement. They have excellent wearability and superb flotation capabilities. The vests provide as much as 16 kg or 150 newtons (35 lb) of buoyancy, compared with 10 kg (22.5 lb) in type I and 7 kg (15.5 lb) in types II and III. In most cases, added buoyancy enables the person to float higher, making it easier to breathe, and reduces the risk of aspirating seawater in rough sea conditions. By keeping the head and chest higher out of the water, it is easier to adopt the heat escape lessening position (HELP) (see Chapter 75). With buoyancy high on the chest, there is also better righting ability and head support. The offshore model can be purchased with an integrated safety harness (Figure 83-1).

FIGURE 83-1 Comfortable, lightweight, and convenient integrated safety harness and water-activated inflatable life vest. It is U.S. Coast Guard approved and features both a back-up ripcord and an oral inflation system.

The U.S. Coast Guard has approved a wide variety of inflatable life jackets, including models listed as type I, II, III, or V. Versions are available with different buoyancies (7.25, 10.89, 15.88, and 27.22 kg [16, 24, 35, and 60 lb]), with and without a safety harness. Water-activated inflatable vests should be worn at all times by nonswimmers, because they might panic after falling overboard; children must be older than 16 years and weigh more than 36 kg (80 lb) to legally wear these vests. Even strong swimmers should consider wearing a water-activated model. Head injury from a surprise fall or an inadvertent jibe might render a person unconscious and leave him face down in the sea with a deflated manual vest. More importantly, any sudden, unexpected immersion can be very disorienting, especially when compounded by reduced swimming ability due to clothing, footwear, and gear. Wearing an inflatable vest that automatically responds to immersion solves the issue of having to find the “jerk to inflate” lanyard. The newest models have inflators that have a single point indicator to show if the vest is armed with an unused CO₂ cylinder. It provides an almost foolproof method for the user to determine whether the life jacket is properly charged and ready for use. The new inflators will not deploy unless the wearer is immersed in water and will not be activated by spray, humidity, rain, or a rogue wave boarding the boat, as some older models have done. All automatic vests have a manual back-up ripcord for inflation, plus back-up oral inflation tube.

Like all mechanical systems on board ship, inflatable vests require regular inspection and maintenance according to the manufacturer’s instructions. Every season, someone should orally inflate the vest (after removing the CO₂ cylinder) and leave the vest inflated for 24 hours to check for leaks. Further advice is to inspect the water-soluble bobbins and replace them as scheduled (generally every 2 years); conduct an in-water test to experience the righting ability of the vest; and prior to each use, unscrew the CO₂ cartridge to make sure the seal is not punctured. One must know how to rearm and repack any inflatable vest according to instructions. Always care for a life jacket as though one’s life depends on it.

Boaters who resist wearing any type of vest may tolerate an inflatable vest packed in a compact belt pack. Carried worn around the waist, it is the least cumbersome of any flotation device. After inflation in the water, the horseshoe-shaped device must be pulled over the head and secured with straps to the chest (similar to the position of a regular inflatable life vest), while the swimmer works to stay afloat; it offers 10 to 16 kg (22 to 35 lb) of buoyancy. This device is not suitable for non-swimmers or children.

When boating in cold weather, a float coat can be worn either with or in lieu of a life jacket. In addition to providing 7 kg (15.5 lb) flotation, the coat offers excellent protection against hypothermia and cushions the rib cage from traumatic injury during a fall.

One should test and wear any new vest in a pond or pool and practice the HELP position. The wearer should float in a slightly reclining position with the water rising no higher than armpit level. Life jackets should be close fitting, with small arm holes. Children require a properly fitted model with crotch straps to prevent the vest sliding up over the arms and head. Common size ranges for children’s life jackets are 0 to 30 lb, 30 to 50 lb, and 50 to 90 lb. The best life jackets for children under 23 kg (50 lb) should have a bi-fold head support and small pillow of flotation in the back to right a face-down wearer and keep them face-up in the water. Some children require a safety harness (see below) to keep them aboard. Never buy an oversized life jacket expecting the child to grow into it in the future. Incorrect sizing of a life jacket compromises usefulness and may have tragic consequences.

An immersion (survival) suit is the ultimate protection from hypothermia and drowning. It blends the properties of a life raft and dry suit. Features include a watertight full-length zipper, watertight hood, face seal for wind and water protection, detachable mitts, neoprene wrist seals, integral boots, inflatable head pillow for optimum flotation angle, water-activated safety light, whistle, and buddy line. Their general bulkiness (one size fits a 50- to 136-kg [110- to 300-lb] person) and built-in gloves make them impractical for continued wear while actively working aboard ship. The Coast Guard now requires personnel on board their vessels to wear a dry suit when ocean water temperature is less than 10° C (50° F), and a less bulky anti-exposure suit with insulating underwear and clothing when temperatures are between 10° and 15° C (50° and 59° F). A type III life jacket is still necessary to provide adequate flotation if a head pillow and flotation are not integral to the suit.

One potential disadvantage of survival suits (as with water-activated inflatable life jackets) is that their buoyancy may impede escape from an overturned craft. The person may become trapped in the cabin, under the cockpit, or under the trampoline of a multihull. “When the trampoline is on top of you, buoyancy is your enemy,” said one multihull sailor, who barely survived after capsizing his vessel while wearing his survival suit. One should always don the suit topside and move away quickly from a rolling, unstable craft. There should be a suit for each crew member when cruising in water below 15° C (59° F). Crew should read the instructions; there is a specific technique and sequence for getting into the suit, pulling the hood over the head, zipping, and closing the face flap. In practice, the suit should be closed and made watertight in less than 60 seconds, inspected regularly for any tears or deterioration, and have the zippers lubricated with Zipper-Ease or other zipper lubricant. A partially closed immersion suit serves only to keep the victim afloat and alive until he dies of the cold shock response or succumbs to immersion hypothermia.

If one has to enter cold water voluntarily (e.g., to free a fouled propeller) without the protection of a specialized suit, take the following steps in anticipation of the cold shock response: Improvise an immersion or wetsuit by dressing in a foul weather suit and snugly wrapping the ends of the sleeves, legs, and waist with duct tape. Wear thermal underwear or insulating fleece under the suit. Stockings, gloves, and a hat will complete the outfit. Pour warm water slowly through the open collar and saturate the clothing covering the torso, then seal the neck. Put on a life jacket and safety harness, with the tether held by an alert crew member. Enter the water slowly, and feel the water seep through all the openings. When breathing is under full control, proceed with the task.

Safety Harness

Always wear a safety harness in rough weather, at night, and whenever on deck alone, out of sight of crew, or when both hands are occupied. In heavy weather, wear a harness even while steering from the relative protection of the cockpit. Adjust the harness to fit snugly around the chest, two inches below the armpits. It should be constructed with webbing at least two inches wide, and have a breaking strength exceeding 1450 kg (3300 lb). Tethers connect the harness to through-bolted deck fittings or to a dedicated jackline, made from either uncoated stainless steel wire or webbing running fore and aft to a through-bolted pad eye or cleat. Designate padeyes or jacklines specifically for the cockpit that can be reached from the companionway, so that crew can clip on before entering the cockpit. The jacklines should be continuous, allowing the crew to roam without having to unclip the harness. Low stretch webbing is preferable to wire and rope because it will not roll underfoot, and tends to lie flat on the deck. Wire jacklines should be inspected for broken strands, and webbing and rope for UV damage and weakening. Marine rope is subject to chafe and to a 50% loss of strength at knots. Tethers should be no more than 2 m (6.6 feet) long with an elastic cover to help to keep them from dragging underfoot; a second tether 1 m (3.3 feet) long helps triangulate support and ensures continuous contact with the ship while changing to different positions. It is also best for use in confined places such as the cockpit and at the helm’s station. Ideally, it should be attached to the boat in a way that will not allow the wearer to be dragged in the water alongside or behind the boat. This may not always be possible. Unfortunately, sailors have drowned while being dragged by their harness and tethers. The shackle at the chest should be a quick-release snap shackle that can be released under load in case the wearer is trapped under a capsized boat. The ship’s end should have a locking snap hook that can be opened with one hand, and not one that will self-release from a U-bolt.

Don the harness before going on deck, and secure the tether before climbing up the companionway. While on deck and underway, hook onto the windward (uphill, upwind) jackline whenever possible. One is more likely to fall down to leeward, and the shorter length of the tether will keep a person on deck instead of dragging him through the water. Women should not adjust the chest strap below their breasts. Injury may occur from the upward force that is placed on the harness when it suddenly comes under tension; some harnesses are designed for females to avoid possible injury. Inflatable life jackets are available with integral safety harness. This convenient combination may be the most important piece of personal safety gear at sea. A harness not only will keep crew aboard and prevent separation from the vessel if overboard but can guide escape from an overturned craft, especially when someone is disoriented.

Crew Overboard

Recovery of Crew Overboard

Do not swim to the boat you fell from unless it is completely disabled and unable to maneuver. Conserve strength and reduce heat loss for the rescue. Whenever possible, get out of the cold water (e.g., onto a capsized or partially submerged boat, or rocky ledge) and stay out of it, no matter how low the air temperature and wind chill effect. Water saps the body’s heat up to 25 times faster than air at the same temperature. Don’t undress. Clothing insulates the body and is relatively weightless in the water.

Time is the critical factor in recovering a person overboard. A well-rehearsed rescue under expert leadership with clear communication during the rescue maneuvers is most likely to succeed. When someone is observed falling overboard, shout “Man overboard.” Designate at least one crew member to spot and point to the victim continuously without losing sight of him (not even for an instant). Floating objects should be thrown overboard, including buoyant cushions, horseshoe buoys, ring buoys, and extra life jackets, in order to litter the water surrounding the victim. The gear may provide extra flotation and will help mark the area for the spotter. Unfortunately, most of these objects will drift faster in winds over 10 knots than a person can swim, so the man overboard (MOB) cannot expect to retrieve a thrown life jacket after falling overboard.

Special equipment designed for locating and retrieving a person overboard should be deployed immediately. This gear should be ready for easy deployment and must release instantly. Too often, the gear is protected against accidental loss by extra wraps of line to the stern pulpit or rigging. Any delay in releasing COB gear will leave it too far from the victim. A crew overboard pole is a 4- to 5-m (12- to 15-foot) floating flagpole that is ballasted to remain upright in rough seas. Without the drogue accessory (a parachute-shaped device to slow a vessel’s drift downwind), it will quickly drift away from the designated area. A man overboard module (MOM) automatically deploys a CO₂-activated horseshoe buoy and a 2-m (6-foot) inflatable locator pole equipped with a drogue and water-activated, lithium-powered light (Figure 83-2). A variety of lights have been developed to serve as rescue beacons. The overboard marker strobe marks the site and illuminates the scene for the rescuers. It automatically activates when thrown into the water. Waterproof personal rescue strobe lights attached to a life jacket can flash for 8 hours at 1-second intervals and are visible a mile away. Other personal strobe lights can last up to 60 hours, with variable rates to conserve battery power. A U.S. Navy whistle has a special flat design to prevent the whistle body from holding water and dampening the sound. Attach one to every life jacket.

FIGURE 83-2 This man overboard module consists of an inflatable horseshoe-shaped buoyant device, a 1.8-m (6-foot) inflatable locator pylon with a light, and a self-opening sea anchor. Both inflatable devices are fully inflated within 7 to 10 seconds after deployment from the canister (usually mounted on the stern pulpit).

Electronic overboard alarms are available for crew; these are small transmitters alerting the mother ship receiver. The personal alarms are activated when they contact the water or when manually turned on (Figure 83-3, online). All onboard GPS units have a MOB function, which, if activated, will create a waypoint at the vessel’s position when pressed. It will also make the waypoint “active,” so the vessel can return to the latitude and longitude of the person at the time of the fall. The GPS is a powerful search and rescue tool, but is not a substitute for maintaining strict visual contact and using signal lights and markers. The inherent small degree of error with GPS in marking the waypoint of the MOB is magnified in heavy winds, large seas, and strong currents, because the person may drift downwind or down-current while the boat returns to the scene. GPS receivers receive signals from U.S. Air Force satellites and then compute the location accurately to within 10 m. It may still be impossible to locate the person in rough seas or during reduced visibility.

FIGURE 83-3 Crew overboard alarms are capable of alerting the vessel’s crew to an emergency, while storing the precise coordinates where the crew member fell overboard.

Rather than rely on the ship’s emergency locator beacon, sailors can wear them on their person. A small unit can be worn (on a life jacket) by a crew member as a personal locator beacon (PLB). Weighing as little as 500 mL (1 pint), and not much larger than a cell phone, it also transmits on the 406- and 121.5-MHz frequencies. The battery life for this compact unit exceeds 24 hours. PLBs do not float upright in the transmitting position. The transmitter requires manual activation and must be held out of the water with the antenna pointed skyward (Figure 83-4). It would be difficult to do this without wearing a life jacket. Some units have an integrated GPS to yield location accuracy to within less than a 91-m (300-foot) radius, versus a 5-km (3-mile) radius from the 406-MHz beacon operating alone. The problem is that most boats, other than professional rescue vessels [or SAR aircraft], are not equipped with a receiver capable of locating the source of the “homer” beacon on the PLB. All PLBs require registration with NOAA. A less technical signaling device designed for night use is the Rescue Laser Flare. This is a handheld light that produces a visible line of laser beam to attract the attention of search boats and aircraft within a 10- to 20-mile radius (Figure 83-5, online).

FIGURE 83-4 Personal locator beacons (PLBs) are now small enough to be carried by each crew member.

FIGURE 83-5 Rescue Laser flare beams emerge as a straight line. At a distance of 10 miles, some models project a vertical line 1100 m (3600 feet) high. The target will see a distinctive large flash of light.

Crew Overboard Maneuvers

The goal in overboard recovery is to return as quickly as possible to the MOB using the simplest maneuver. Begin the process immediately. A boat traveling at a speed of 8 knots moves away from the MOB at about 3.9 m (13 ft)/second or 244 m (800 ft)/minute. At that rate, one-half a mile is traversed in 3 minutes. Motorboats should reduce speed and return in a simple circle. Sailboats under power alone can return by simply circling back and approaching downwind of the victim. Establish contact by using a heaving line, such as a floating polypropylene line in a throw bag. If the boat is drifting downwind, slowly advance forward to complete the recovery over the leeward side, being careful to not drift on top of the victim. Sailboats under sail should approach on a close reach, which allows the vessel to speed up or slow down as necessary by changing course.

The “quick stop” recovery maneuver is designed for rapid MOB recovery. This method enables the boat to reduce speed immediately by turning into the wind while trimming in the mainsail and keeping the headsail (jib) aback. Thereafter, the helmsman keeps the boat turning downwind while steering to remain close to the victim. After passing abeam of the victim, the jib is dropped (or furled), and the boat heads up to the wind (on a close reach) to stop alongside the victim at an angle of about 60 degrees to the wind with the sails luffing (flapping into the wind). By sailing the final approach to the MOB on a close reach, the sails can be fully luffing or trimmed in to maintain forward movement if short of the mark. The technique is similar to picking up a mooring under sail. The boat can also be left beam-to-wind with the sails luffing while contact is made with the victim. The engine can be started and left in neutral, ready to be used if needed in the final approach. Rescuers must ensure all lines are aboard before engaging the engine, to avoid fouling the propeller. It is advisable to return to neutral when close to the victim. The main danger to the victim is being sucked under the stern while the propeller is turning and the boat is moving forward under power.

The direction of approach to the victim used by the rescue boat is controversial and involves judgment based on many variables, including the sea state, wind strength, drift of the boat relative to the victim, maneuverability of the boat, and condition of the MOB. If the seas are large, approach to leeward (downwind) of the MOB so the boat cannot fall off a wave and injure the person in the water. Gentle seas permit an approach to windward (upwind) with a slow drift down to the victim. The boat will always drift faster than the person in the water, so have retrieval gear ready.

An injured, hypothermic, or unconscious person (not waving or looking at the rescue boat) requires assistance by a rescue swimmer, who should take steps to avoid the cold shock response. The rescue swimmer should be tethered to the boat during recovery of the MOB. Ideally, the rescue swimmer should be trained in water rescue and lifesaving techniques and be able to recognize the warning signs of panic as he or she approaches the victim. If the MOB is unconscious, assume possible head and neck injury, and stabilize the cervical spine before hoisting the victim out of the water. The life jacket itself may be used to control the head and neck if it is tightened in the upper chest area.

The goal is to have the MOB back on the boat as quickly as possible. Practice the different techniques and decide which method and modifications work most effectively. The Lifesling, developed to enable one person to retrieve a person overboard, is a flexible floating collar that doubles as a hoisting sling (Figure 83-6, online). Deploy the collar from the stern pulpit and deliver it by repeatedly circling the victim, much as a ski boat maneuvers to deliver the towrope to a fallen water skier. After securing the horseshoe over the head and under the arms, pull the victim back to the boat and hoist him or her in the apparatus with the assistance of a halyard and winch (Figure 83-7). Lifelines are an obstacle to bringing the MOB back on deck, but are an important source of protection for the remaining crew. You may elect to secure lifelines at the stern (or transom) with lashing rather than shackles or pins so they can be easily cut and released in a recovery should the need arise.

FIGURE 83-7 Successful rescues of a crew overboard requires consistent methods for contacting the victim, and for getting him or her back on board.

FIGURE 83-6 The Lifesling has become the preferred man overboard recovery system. The flotation horseshoe collar with attached retrieving line can be thrown or towed to the overboard person and used as a lifting sling to hoist the crew member back on board. An inflatable model comes in a throw bag.

If the crew has lost sight of the victim, immediately call for assistance. A mayday call on VHF-FM channel 16 will notify the Coast Guard and simultaneously alert all ships in the area monitoring this channel. The last known position should be obtained using GPS or reference to any navigational buoys and landmarks on shore. Rescuers should perform repeat searches of the area, because it is easy to miss someone in poor visibility or choppy seas. The victim will be far more likely to be located if he has the correct gear. Ideally, this includes a high-visibility (orange or yellow) life jacket with reflective tape combined with a safety harness, personal strobe light, loud whistle, packet of waterproof self-launching meteor flares, fluorescent dye marker, and a PLB or other crew-overboard alarm. Perhaps the most important factors for a successful rescue are the crew’s familiarity with the boat and the MOB equipment, and their teamwork, leadership, and expertise developed from practicing the maneuvers. A full review of the 2005 Crew Overboard Rescue Symposium conducted on San Francisco Bay can be found at http://www.boatus.com/foundation/findings/COBfinalreport. This study reviews the challenges for a successful recovery, required skills of the crew, preferred recovery maneuvers, and equipment that can be helpful in locating and retrieving the victim. It is a “must” read for every boater. It is also available in a slightly different format from U.S. Sailing on the website http://www.ussailing.org/safety/Studies/COB.pdf.

Flooding

Flooding, and the potential for sinking, is a threat to every boater. Boat U.S. Marine Insurance examined 50 claims from recreational boats that sank while underway, ranging from a tiny personal watercraft to a 16.5-m (54-foot) ocean-going sailboat. The full report is on the website at http://www.boatus.com/foundation/guide/index.html. Thirty-four percent of the boats sank because of leaks at thru-hulls, outdrive boots, or the raw water cooling system/exhaust. The single most critical reason small motorboats flood in open water relates to transom height. Engine cut-outs may be only inches above the waves, and the motor well may not protect the cockpit. Often, weight distribution of passengers and gear to the stern contributes to the problem.

Flooding may occur from failure of systems or construction (6% of the boats sank after coming down hard off of waves and therefore splitting open), or structural damage from collision and extreme weather (Box 83-1). Before abandoning ship, quickly assess the damage. The limiting factor is time. Stock the proper tools and repair supplies in a damage control kit (Box 83-2), and know how to respond quickly and skillfully. Assign duties to the crew before departure so that they know what to do in the event of flooding (and crew overboard, fire, grounding, and dismasting). Duties include damage control, radio transmission of a Mayday (can be cancelled later if necessary), and preparation to abandon ship.

Early detection of flooding is crucial for an effective response. Make frequent visual inspections of the bilge, engine room, galley, and head while underway, and maintain watertight integrity at all times. The most reliable way to keep a boat afloat is to keep the water on the outside. Hatches for the main companionway, engine room, lazarettes, cockpit lockers, fish holds, and elsewhere require gaskets and proper dogging (locking) devices to ensure watertight seals; secure them while underway. Boats flood from the top down as well as from the bottom up! After a knockdown or wave breaking over the cockpit, water may go straight below decks if the companionway drop boards are not in place. These boards require robust dead bolts capable of locking from both sides. Severe flooding, with damage to the electronics, navigation station, and engine, usually results from top down flooding.

Discharge plumbing requires seacocks. Regularly inspect through-hull fittings, the engine drive shaft stuffing box, clamps, and hoses. Avoid using polyvinyl chloride (PVC) or any other domestic plastic plumbing fittings for through-hull fittings below the waterline; they can easily break off or fracture if struck by shifting stores. The preferred materials are Marelon (reinforced plastic) or bronze, together with stainless steel hose clamps. Post a diagram in the cabin showing the locations of all through-hull fittings and the routes of connecting hoses. Keep seacocks accessible and unobstructed and be able to find them blindfolded. Install U-shaped antisiphon loops above the highest waterline (it changes as the boat heels). Without these loops, water can siphon back through the hose and into the bilge.

Reliable bilge pumps are the best defense against flooding (Figure 83-8, online). An excellent pump can buy time for locating and plugging the leak. However, no pump, manual or electric, can keep up with even a modest-sized hull breach. If a boat is equipped with an automatic bilge pump (or pumps), install a cycle counter on the pump and an “on” light to alert the crew when the pump is activated. A second emergency pump mounted above the first, using a separate float switch, can provide added pumping capability if the first pump cannot keep up with the leak. In this case, an alarm installed in the circuit can alert the crew to flooding.

FIGURE 83-8 Large vessels may elect to have substantial emergency pumps onboard, which can keep up with flooding from modest hull breaches. Note also the crew overboard device on the pushpit and the throw rope.

Keep the bilge clean and free of debris to avoid clogging the pump strainer. Perform regular inspection and maintenance of the entire pumping system. Aluminum-body bilge pumps corrode from the inside out, especially while retaining saltwater. They may appear to be in perfect condition, yet be completely useless. Hoses crack with age, rubber components become dry and brittle, valves jam, and moving parts deteriorate through wear and corrosion. To guarantee reliability, disassemble, inspect, and clean manual bilge pumps annually. Bilge pump handles should be easily accessible and secured with a lanyard in the vicinity of the pump to avoid loss after a knockdown or rollover. Offshore boats require at least two manual bilge pumps, one operable from above decks and one below decks. Know the capacities of the boat’s compartments and have a means to pump out any that flood. Test the pump’s capabilities by intentionally flooding the bilges (preferably with fresh water), and monitor how long it takes to pump out the water.

The volume of water rushing in depends both on the size of the breach and its depth below the waterline. A 2.5-cm (1-inch) diameter hose disconnected from a seacock 30 cm (1 foot) below the waterline allows 75 L (20 gallons) of seawater per minute into the cabin; a disconnected open seacock the same diameter just 60 cm (2 feet) below the waterline admits three times that amount of water. A boat equipped with the largest manual double-action twin-diaphragm bilge pump can pump a maximum of 36 gpm, a limit easily surpassed by the examples given. It is therefore critically important to locate and stop the leak, rather than fight what may be a losing battle by pumping to prevent sinking.

As the water rises in the cabin, a leak becomes more difficult to locate. The inflow rate decreases as the depth of water in the boat increases, because the pressure gradient is reduced. At a critical level of flooding, the inflow rate may slow sufficiently to allow pumps to handle the volume, so do not stop pumping. A point of zero net flooding may be reached from the inherent buoyancy of the boat as it settles in the water (another reason the ship should not be abandoned unless it continues to flood). Many small wood and fiberglass boats float when fully flooded or swamped. Boats less than 6 m (20 feet) in length constructed in the United States after July 1972 are required to have sufficient built-in flotation to remain afloat when swamped. Small boats (e.g., daysailers, small open motorboats) can obtain additional buoyancy by lashing down unused life jackets, cushions, and fenders to increase flotation.

A tapered, soft, dry wood plug sized to fit a leaking through-hull fitting can serve indefinitely as an adequate seal; it will swell to seal the fitting or any small puncture in the hull. Take the plugs out of the damage control kit and attach them to their respective through-hull fittings with lanyards; this will make them instantly available and help the crew find them in the dark. Forespar’s TruPlug is a new damage control product. It is a tapered circular cone-shaped plug about 23 cm (9 inches) tall and 12 cm (4.75 inches) across at the base made of foam that is a spongy but firm cellular material, and is coated with a flexible sealer adding strength and color. It can be used as a temporary or emergency plug in boating applications where water would enter a circular, oval, or irregular hole caused by emergency mechanical failure or hull breach due to impact. Its ability to be twisted or jammed into irregularly shaped holes gives it an advantage over tapered wooden plugs.

Large holes can be overlaid with a collision mat (Figure 83-9) placed outside the hull to supplement a temporary interior patch (see below). The mat is a piece of heavy canvas or vinyl-coated fabric with grommets and lines that enable it to be positioned and secured on the exterior surface. It is held in place by pressure and lines. Collision mats can be purchased or improvised by using a small sail or awning material, although it is a mistake to make the mat too large; generally 1.2 m (4 feet) on an edge of the triangular shape is adequate. The water pressure automatically spreads the patch over the hole to form an effective seal and holds it in place. A commercial hull repair kit features flexible oval concave sheet metal plates with rubber gaskets. A bolt is welded to the intended exterior piece. The idea is to slip one oval through the hull breach, then back it from the inside with the second metal plate and tighten both together with a thumbscrew.

FIGURE 83-9 Triangular patches made from coated fabrics can be held in place with lines attached to each corner.

Lacking special equipment, any soft, pliable material, such as a life jacket, mattress, blanket, towel, cushion, clothing, or foam pad, can be used to slow water rushing through a jagged break in the hull. When placed against the exterior hull, the suction effect created by flow and hydrostatic pressure will generally provide some clamping pressure to the plug or patch. If a plug is positioned from inside the cabin, shore it with a board and brace it with a pole (e.g., oar, mop handle, boat hook, whisker pole, strut, bunk rail). The eventual solution to a hull repair may start with a crude internal patch to slow the flow of water and buy time, followed by an external patch, followed by an improved internal patch with plywood and bracing. The vessel’s pumps may then be able to handle the remaining leaks.

Underwater patching compounds can be used to bond a solid plate over the hole or to impregnate an expandable material or packing to serve as plugging material. There is great variability in cure speed, ease of mixing, mixed viscosity, and adhesiveness. Some products work only on specific hull materials (e.g., wood, fiberglass, or aluminum). Supplement repairs with other measures to help slow the inflow. Heel the boat away from the area of damage to decrease hydrostatic water pressure. This is easy to accomplish under sail. For powerboats, shift heavy items to the side opposite the leak and slow forward speed if water is entering a hole in the bow.

When ingenuity and improvisation fail to stop flooding, the U.S. Coast Guard can supply a portable gasoline-powered dewatering pump to assist a sinking vessel. The unit is simple to operate and comes in a waterproof barrel with hoses, gasoline, and illustrated operating instructions. When dropped from an aircraft into the sea, a retrieving line will be also dropped to the deck crew. It takes two people to lift the barrel from the sea onto the deck. The standard CG P-1B dewatering pump can pump 120 gpm at 3-m (10-foot) lift, and is capable of running 4 to 5 hours on a tank of gas. The P-1B pump, known as the “drop pump,” is likely to be carried by helicopter and by any of the various Coast Guard rescue craft. A larger pump, the CG P-6 (classified as a dewatering/fire fighting pump) is carried by Coast Guard search and rescue ships and is placed either onboard or passed via lines, depending on weather conditions. Pump capacity is 250 gpm at 3.6-m (12-foot) lift; it runs 4 to 5 hours on a tank of gas. Both pumps are dramatically more effective than even the most robust manual or electric bilge pump. However, 250 gpm is equivalent to the inflow of water from a 3-inch hole (a relatively small breach) only 60 cm (2 feet) below the waterline; any larger hole at this depth will exceed the capacity of even the P-6. Remember to run either pump outside, not in an enclosed space where carbon monoxide may accumulate. Refuel them only after the engine is stopped. As with all safety equipment, these pumps can be confusing to operate for nonprofessionals, especially at night with a boat that’s threatening to sink from under you. Attendance at a Safety at Sea seminar or other survival training is highly recommended as a way to become familiar with infrequently used safety gear.

Some oceangoing cruising vessels are built with watertight compartments to confine flooding to a limited area. Maintain watertight bulkheads. Know the locations of watertight doors and how to operate them.

If flooding and sinking are inevitable, the captain should consider running the boat onto shore.

Fire