Hypothermia, the lowering of a person's core body temperature, can be a killer for anyone who works or plays outdoors. Boaters operating away from shore in cold weather have little chance for survival if they fall overboard or have to abandon a sinking ship. Humans rapidly lose body heat in cold water and can die in a matter of minutes.
Immersion suits, or survival suits as they are often called, can significantly improve survival time in cold water. These suits are often featured in stories about successful sea rescues. Recognizing that hypothermia is a major factor in lives lost at sea, the US Coast Guard now requires immersion suits on documented vessels operating north of 32° North and seaward of the Coastal Boundary Line.
Even when not required, immersion suits are recognized as an important piece of life saving equipment for boaters operating in cold waters. To be effective, suits should be stored and maintained according to the manufacturer's instructions, must be readily available and crew members should know how to use them.