The tour in itself is ok, but Waikiki does not seem to be the right place for snorkeling. The water is not clear enough to see the fish properly. I got a very hazy view of the fish and we went in the morning (which is supposed to be the better time). We did see a few turtles but they were on the surface of the water. There was no need to snorkel to see them.
Waikiki is SO crowded, you are always bumping into another person. People were fed up of waddling about in the water in less than an hour.
The guides were nice but they did not give great instructions. We have snorkeled before so we knew how to, but not great for a first timer.