First off, let me say we had an overall good time. They take you to the usual places, where you can see some great stuff snorkeling. Also, they were able to locate some spotted dolphins for us, which was one of the highlights of our trip (though they refuse to allow snorkeling if they see dolphins in the area). That being said...
I would definitely go on a larger boat if I were to do this type of excursion again. While they make a big deal of only having a limited number of people on each trip, it does not matter if the boat is so small; we only had 12 people on the zodiac and it was a tight fit. More importantly, though, was that the ride back was *terrible*; the small boat was really slammed by the waves, making it a literally painful experience. Think very hard if you really want to do this in a zodiac. In a larger boat, you have easier access to your camera, etc. (in a zodiac you need to put everything into a common locker, which is not trivial to access).
Remember, all of these tours will show you some great snorkeling. I would just highly suggest you go with an operator that has a standard sized boat, rather than going with a tiny zodiac.
If you own or manage Ultimate Whale Watch, register now for free tools to enhance your listing, attract new reviews, and respond to reviewers.