If the life guard sees you drowning but decides to play a game on his phone, that would be gross negligence.

If the life guard jumps in the water and brings you to shore, but forgot to keep your head out of the water the whole time so you still drowned.  That would probably be negligence.

Regardless, what this is going to result in, is the City and State closing down a lot of beaches or completely eliminating life guards and saying, swim at your own risk.  By closing down the beaches, only the victim will be to blame if they drown.  Whereas, if they have life guards, the City and County will be sued.