At 26 degrees one is in the severe zone with coma and dilated pupils being seen. Ekg becomes flatline at 19 degrees. Oxyhemoglobin dissociation curve shifts to the right in hypothermia. Buffering system in the body is not as effective in hypothermia. Cold water immersion - heat is transferred 25 times faster than in air.
Clothing helps to prevent heat loss - hence keep clothes on if able.
Alcohol effect causing peripheral dilation is extinguished when cold water immersion occurs. It is advised to stay still in the water if there is no reason to move. Early drowning occurs from cardiac arrhythmias, respiratory reflex gasp and hyperventilation, and muscle dysfunction interfering with the ability to swim and keep the head up out of the water. Do not ambulate the patient if possible - this leads to blood being cooled in the extremities. Important to get a core temp probe in place.