Since it was free, we decided to take the CTI glass bottom boat tour. The boat has a number of windows in the bottom of the boat, so there you actually could see fairly well, though there wasn't a lot to see. We saw some brain coral, sea urchins and a few fish and a skate deep down on the ocean bottom. The reef is largely dead, probably a result of recent hurricanes. We were a little squished in the boat. Everyone wears life preservers and I have long legs which were crammed against the railing. By the end of the trip I was pretty cramped. One woman got sick and puked over the rail. Not sure if she was seasick, or if she maybe had a hangover. Another woman was also motion sick. Just wanted to make you aware in case you are prone to motion sickness. More interesting than what you see in the water is the tour of the homes and resorts along the shore. You will pass Couples San Souci and some magnificent homes, one that supposedly belongs to Mick Jagger. I thought it was worthwhile. Based on this trip, we decided not to go snorkeling do to the lack of interesting things under water.