We did this the last day in Bermuda. We did this through Dolphin Quest. If you have the extra money, DO IT. You're only there for a half hour but it does feel like longer. The trainers are great, we had Christa. We bought 3 of our pictures ($48) and don't regret it. It's a once in a lifetime opportunity. It was my boyfriend's life goal so we were happy about that.
We did this the first day in Bermuda. The tour was through Fantasea. It was AWESOME. Tour guides were GREAT! 20-somethings with a college-kid vibe, but they are natives to Bermuda so they told us a lot of helpful hints. They give you rum swizzles too! I got sea sick when it came to looking at the glass bottom, but Seabiscuit (one of the tour guides) immediately gave me a ginger ale before I even realized I was getting seasick. They were awesome & gave us a lot of one on one inside info. Nice kids & great tour. You also see a ship wreck and really see the ocean. Not something I would do again as it isn't necessary but it's definitely something I'd recommend to anyone who has never been to Bermuda or who has been 100 times!