"The U.S. Navy Diving Manual has this to say: Hypothermia is easily diagnosed. The hypothermic diver loses muscle strength, the ability to concentrate and may become irrational or confused. The victim may shiver violently, or, with severe hypothermia, shivering may be replaced by muscle rigidity. Profound hypothermia may so depress the heartbeat and respiration that the victim appears dead. However, a diver should not be considered dead until the diver has been rewarmed and all resuscitation attempts have proven to be unsuccessful. For navy literature, these might pass as reassuring words: you are not dead until you are warm and dead."
— Cold: Adventures in the World’s Frozen Places (Bill Streever)