The person who did the talk on was very knowledgable but it still wasn't very interesting. Water was murky and their really wasn't much to see. Maybe on a better water day it would have been better?
I think this would have been a great place but we didn't arrive until early afternoon. We did go snorkeling at Chankanaab. It was a nice place and there were very few people there....perhaps because it was raining? There is a fee to get in and we didn't do any of the other activities except snorkling. If this is all you want to do, you might try Playa Corona instead. No fee to get in, but they do expect you to order from the bar. By the time we got back from snorkeling it was early evening so that was pretty much the end of our day. I'm sure had we arrived in the a.m. instead of mid day we would have gone and found other things to check out. Looked like a cool place.