Loonbath

To do a plank over your bathtub, and thust into the water repetitively until orgasm is reached.

Hey did you see the smile on Jims face, he must have went loonbatheing last night.

Loon-bathing

The act of planking over a full bathtub and repeated plunging your erect penis into the water until you cum.

Noah Stone likes loon-bathing every night because he gets no pussy.