Exposure of the head and chest to cold water causes sudden increases in heart rate and blood pressure that may result in cardiac arrest. Other responses to cold water immersion result in immediate loss of consciousness and drowning. The crisis is more serious than these numbers suggest. Any movement in the water accelerates heat loss. Survival time can be reduced to minutes.
Hands become numb and useless.
Without thermal protection, swimming is not possible. The victim, though conscious, is soon helpless. Without a life jacket, drowning is unavoidable. Once in the water Try to get back in or on your boat immediately. Do not leave the boat .