I went on a very similar tour in cozumel which is a dunebuggy tour. Both follow the same route which is a 90 minute ride along the coast of the island. The ride will be a mixture of beach sand and hard dirt / rock. After a while, you will arrive at the beach, have lunch then get about 45 min of snorkle time. Then a 90 min ride back. The dune buggy tour was a total blast, the buggys were converted VWs. Another option is a jeep tour which also does the same route.
We did that tour and it was a lot of fun. The ATV are standard though. They teach you how to drive them. It started pouring while we were on the trail and we got soaked, but still fun. Also when we got to the beach we couldn't snorkel, because the water was too rough.
You can book the tour through a few places. I booked from the cozumel homes website. The good thing about this tour is that the departure point is only about a 5 min walk from the pier (providing you dock at the pier in the center of town) http://www.cozumelhomes.com/ go to the tours tab.