Works great offshore, not so sure about inshore...
A couple of cases of cheap beer are far better currency than dollars when those guys have been bouncing around in the hot gulf for 2 weeks.
I guess you could circle an anchored boat a few times and see if someone comes out. Doubt it would be worth their time though. The Deal you are looking for would probably be somewhere between wholesale and retail and I'm not sure if it's worth the hassle for the shrimper.