Basically a euphuism for anal sex.
Dude 1: Look at that sweet piece of round ass over there...
Dude 2: Who the new chick? Yeah she has a bubble booty alright...
Dude 1: So are you thinking what I'm thinking?
Dude 2: Yep, she's a perfect candidate for some world class s**t digging...
Dude 1: Aight then...watch me go over and get them digits!
Dude 2: Play on player...play on.