Human Beings and the Cold
Hypothermia: Hypothermia is called the silent killer and can happen even if you don't capsize or get wet. Hypothermia occurs when the body core temperature begins to fall below its normal 98.6°. Wind, rain or sweating can lead to hypothermia.
With slow onset hypothermia as the core temperature drops below 97° shivering usually starts and you might feel your hands and feet are cold (even if properly covered). This is why its said that, if your feet are cold, put on a hat. To preserve core heat, the body will slow the circulation of blood to its extremities, so they get cold first. This is one of the hypothermia warning signs. It should not be disregarded. Even at this early stage, hypothermia is very dangerous. The loss of dexterity can make it impossible to open a hatch for extra clothing, or you might be unable to use a paddle float to do a self rescue, and many kayakers have not been able to put their spray skirts back on. This can happen even with the best hand gear made. As stated, it isn't improper hand gear, but the bodies survival instinct of slowing circulation to the extremities.
As the core temperature drops to the lower nineties, shivering will slow or stop and the person might begin to feel warm again. This is when the real danger begins. The loss of mental alertness will occur, causing wrong decisions to be made. The victim will lose coordination, increasing the likelihood of a capsize. At this stage it becomes very difficult to warm the person safely outdoors, or for the person to save themselves. The victim's body will not be able to warm itself.