I was very disappointed with this activity. I read some reviews before signing up and I surely had a very different experience. I went the end of October on a night that included a buffet dinner and open bar. The price (without transportation) was $80. The snorkel adventure started out from the shore - we were led to believe that we would be going out on a boat. Wet suits were not offered. At least three people had trouble with equipment that was given to them - flashlights that went out, masks that leaked. The snorkel lasted about an hour, it was ok but really nothing special - you see more during the day. The best part was the bioluminescence in the water which was pretty good but we lucked out with a moonless night.
After snorkeling we went across the island to Hull bay (about 45 mins away) for a buffet that was very poor (fried chicken that was dry, fish that was overcooked, salad that was cukes and lettuce, corn that had been over cooked and spicy pasta salad) and the open bar - a large bottle of rum and beer. We asked for wine and they said there was none included. For $80 it was not worth it! Oh if you don't snorkel for $40 you can join the group for the buffet and open bar.
There are many other activities on St Thomas that are far better than this - I felt totally ripped off