Just back from the magic island, and can highly recommend renting the boats if you are looking for a relaxing day out. They are quite small, but we had 4 lads on each one quite comfortably, and really enjoyed the time. We took the afternoon session to incorporate the sunset, which was amazing, floating on the sea, with the tunes from Del Mar, all the people on the beach and the sunset was a wonderful experience. I would also recommend stopping off at the cave half way through the route, and doing some cliff jumping, we bumped into some Italian guys and spent the next 2 hours trying to outdo each other.
One word of warning, it can get a bit choppy the further out you go, so if you suffer from sea sickness, this isn't the trip for you.