When you shove your dick, both balls, and both fists in a girl's asshole.

The act of inserting one's entire penis and scrotum into an anus or vagina. The difficulty of that feat is akin to getting three dogs to take a bath at once, hence the phrase 'three dogs in a bathtub.'

You're screwing a girl in the ass. You try to get your nuts up in there as well. It's about as tough as trying to get the dog into the bathtub.

When a guy and a girl sit at the opposite ends of a bathtub and the guy turns around and puts the water spicket up his ass. Then turns the water on full blast and leaves it that way until he is so full of water he can’t hold it and the pressure is pushing him off the spicket. He then turns around and blasts his girlfriend with his ass water.

In Southern States a euphemism for clitoris is "the man in the boat" referring to the lone passenger in the dory shaped vulva. Many newly weds are determined to sink him. " Fatman in the Bathtub with the Blues" is a reference to an engorged clitoris in need of attention.

A euphemism for sexual activity

simons mum