Floating pie

When an older woman goes swimming and forgets the
bottom of her bathing suit. While she's under water
her floppy vagina floats to the surface.

also known as:
the hovering cake
the soaring patty
the unsinkable muffin

Where's grandma? I've been looking for hours
and can't find her. What's that? It looks like a floating pie. Wait a minute, that's grandma! I found her!