We had done a tour from the Jet Ski place right there on the dock. We had a blast. They have 3 tour guides that go with a group of 10. IF memory serves me right, it was about $100 for two of us on one jet bike and the tour lasted about 2 hrs. They stop at areas around the island and give info about the area. WE also went to a sand bar in the Atlantic and did a little swimming.
The guide did mention the risk of other jet skiers and boater not yielding, so to keep your guard up when leaving and coming into the dock area, and my BIL had a close call with another jet ski (not part of the tour).
Hope this info helps. Also if you chose to do this, the guides are tipped, and in our case it was well deserved, I just wish I would have had a little more $$$ with me to tip them, they were awesome.