Yesterday I ran across this short article about a beluga whale saving a diver who had become paralyzed (it was in an aquarium tank). Anyway, I didn’t think much of it until today, when I was reading The Selfish Gene and ran across this explanation:
Whales and dolphins drown if they are not allowed to breathe air. Baby whales, and injured individuals who cannot swim to the surface have been seen to be rescued and held up by companions in the school. It is not known whether whales have ways of knowing who their close relatives are, but it is possible that it does not matter. It may be that the overall probability that a random member of the school is a relation is so high that the altruism is worth the cost.
Apparently there are quite a few stories of dolphins and whales saving drowning people.