Similar to the Bases in Baseball.
If you go all the way around the world, well guess what, you've had sex.
The other stages are up to you. You can pretty much make it up and Elaborate as you wish.
"So, are you sailing your boat this weekend?"
"Ya, but were just going to an Island off the coast"*Wink Wink*
"You Let Your Anchor Up?!?!?! You Slut!"