Tanning naked with an erection to avoid embarrassing penis wrinkle tan lines.
Dude 1: Yo, why are you laying by the pool naked?
Dude 2: I'm tanning my penis.
Dude 1: Don't you know you can only get a nice even wang tan
when you have a boner? Rub that into a sundial.
Dude 2: Shit. good call.
Dude 1: What time is it?