What they teach you in the navy to be useful to your comrades... And prison. It's stuff you do revolving around a boat, or a metaphoric boat. Definitely no second meaning.
A good example of it's use would be
"Hey soldier, have they taught you boatt stuff yet? You need to get that down if you're gonna survive here."
or
"Hey homie, I know you've learned boatt stuff, come show me how it's done >:)"