Do wild snakes live together in this manner?

this is a behavior during the mating season of garter snake. they are mating, and they're non-poisonous. the only other snake that groups together like this is the water moccasin, and for different reasons. their young are born in the water, and they pool together. this is a dangerous thing to fall into, because if you do, you're bound to die as babies are more venomous that adults, more less they can't control their venom output, and thus attack in a frenzy. so, tell your friend not to swim in freshwater lakes until late July, especially in the S.E. United States.