Xel-Ha
Behind me is the entertainment complex of Xel-Ha and the start of the snorkeling area.
All told we probably snorkeled 2 to 4 miles in the inlet! There were lots of fish, including some huge 25 pound slow fish (they looked like the kind of fish that would eat dirt!) hanging out near the sand bottom in the middle of the inlet.
You can snorkel up the inlet to where a river/stream flows in and either swim, walk or float back in inner-tubes. Along the way, there are diversions such as cliff diving, and rope bridge to climb on.
The entertainment value of Xel-Ha is very good. In addition to the good quality snorkeling, there are parrots and monkeys to take pictures with and a place to sleep in hammocks.
They sell the entrance tickets at a booth outside of the Tulum Ruins for 10% off, and Saturday and Sunday are discounted even more. Our Saturday tickets cost $22, the normal weekday rate at Xel-ah's gate is $27. They also have an all inclusive package that includes food and the like, which would be fun if you could get there early, snorkel, eat, nap in the hammocks, maybe have a drink and then walk around for a few hours.