After retrieving a man from a cold sea there is always a large chance of him going into shock. It is therefore a good rule to have the person, regardless on how well he may look, recline immediately in order for the blood circulation to the head become normal as soon as possible. If possible, put him in warm and dry clothes as well to place him in a warm room.
Unconscious man should be lifted in horizontal position when possible.
Futher material concerning the treatment of hypothermia should be read, for example, “Survival in Cold Water”, published by IMO, or translation of that booklet in your language published by the local authorities.