Used to be very common in urban pools during the late 80's, early 90's. A posse of ne'er-do-wells would pin girls up along the side of the pool or just circle them, and then feel up or rape them. It got so bad that NYC had a goofy public service ad that went something like "Don't dis your sis at the pool, that ain't cool."
Nothing stopped till angry boyfriends, dads, and brothers started shooting and stabbing the little assholes.