Many boating-related fatalities and drownings are a result of cold water immersion. After a person falls into cold water, both the temperature of the water and the amount of time the person is in the water affect the way the body physiologically responds.
A vessel capsizing and falling overboard are the leading causes of cold water immersion. Capsizing is most often caused by improper boat handling, poorly secured loads, overloading, improper anchoring or loss of power/steerage.
In order to prevent cold water immersion, be sure not to overload vessels. Always take weather and water conditions into consideration when operating. Falls overboard can further be avoided by remaining seated and limiting how much you move around a boat when it is underway.
Stages and effects of cold water immersion
Stage 1 - Initial immersion - Cold water shock
If a person falls into cold water their body's initial reaction is shock. Also known as a gasp reflex, shock can include hyperventilation and muscle spasms. This initial reaction can result in water inhalation as well as significant changes in heart rate and blood pressure. These initial effects are present for the first two or three minutes of immersion.
Stage 2 - Short-term immersion - Impaired function
In cold water, a person may begin to experience the loss of basic motor skills after only a few minutes. Between 3 and 30 minutes after immersion a person's hands quickly lose strength and sensation and subsequently their ability to swim (even for strong swimmers). In cold water immersion cases, boaters often drown as a result of swimming failure before hypothermia has the chance to set in.
Stage 3 - Longer term immersion - Immersion hypothermia
Following 30 or more minutes of immersion, hypothermia (a drop in body temperature below the normal level) will begin to set in. The person’s overall body temperature will continue to drop until it reaches the same temperature of the water. As the body's core temperature falls, a person will eventually lapse into unconsciousness.
Stage 4 - Post-rescue collapse
A drop in blood pressure which may lead a person to become unconscious or to stop breathing at the point of rescue or up to several hours afterward. Death may occur within minutes to hours post-rescue.
Surviving cold water
If rescue is not imminent, your number one priority is to get yourself out of the water as soon as possible. You can do this by climbing onto your capsized boat or any other floating objects, or by swimming to shore if it is within reach. The sooner you can get your body out of the water, the greater your chances of survival are.
If you manage to make it to shore, be careful not to try and stand up if the current is too strong. Doing so can result in a shallow-water drowning. This type of drowning is where a person's feet get caught in rocks or sand at the bottom of the water, and the strong current forces the upper body underwater, causing the person to drown.
If rescue is imminent you should conserve energy and body heat as much as possible. You may extend your survival time by wearing your lifejacket.
H.E.L.P. (Heat Escape Lessening Posture): This position aids in keeping as much body heat as possible from escaping. If you are alone, cross your arms tightly against your chest and bring your knees up close to your chest
If other passengers are also in the water, use the huddle technique to maintain everyone’s body heat. Maneuver so that the sides of your chests are close together with arms around each other’s backs and legs intertwined.
Additional cold water protection:
- A floater suit: full nose-to-toe PFD (Personal Flotation Device)
- An anti-exposure work suit: PFD with a thermal protection rating
- A dry suit: suit used in conjunction with a PFD and a thermal liner
- A wet suit: suit that traps and heats water against your body
- An immersion suit: suit used in extreme conditions (usually off-shore)