My wife and I took the Carribean Spirit tour out of Bayside and thoroughly enjoyed it. A nice boat, great views of Miami, excellent (real!) sailing, plus the added bonus of anchoring in a protected area for swimming and snorkeling. Crew of Capt Terry, Diego, and Guillermo were friendly and helpful. We winter in Miami every year and this was one of the better attractions we've participated in. Highly recommended.
Be sure to take bathing suit and towel, and a sandwich/snack. Free bevs on board.