Mom never worries about her top or bottom falling off. She only swims at clothing optional beaches. And if she can't find such a beach, she carries, in the trunk of her Yugo, a large sign saying

CLOTHING OPTIONAL BEACH!
IF NUDITY OFFENDS YOU,
JUST FUCKIN' LEAVE!

that she sticks in the sand. Nobody gets to tell Mom where she can and can't get some sun on her buns!