My DH & DS did a deep sea fishing excursion in St. Martin through Shoretrips.com. My husband could not say enough good things about Rudy - extremely clean boat, very knowledgeable, and they had a great time (and he's very picky!!) I believe that Rudy only takes 4-6 people so it's very private too. Paste & cut this link:
Or if that doesn't work, just go to www.shoretrips.com, click on St. Martin, then deep sea fishing. I've used this website a few times and they're great. They'll answer any questions you have.