Heat loss in water is increased 25-fold. Water below the temperature of 28° C (82° F) can be considered as cold. The degree of hypothermia depends on exposure time, water temperature, insulation and more.

Hypothermia is a condition in which the core body temperature falls below 35° C (95° F). The symptoms prevailing in mild hypothermia (35° - 33° C) are confusion and shivering In moderate hypothermia (33° - 30° C) shivering is replaced by muscle stiffness, the level of consciousness falls rapidly, blood pressure drops and pulse rate falls.

In severe hypothermia (<30° C) the main findings are coma, absence of reflexes, and progressive depression of heart rate and respiration with deepening hypothermia.