When we were at Cancun about 2 yrs ago there was a very nice man who had a beach based business of renting jet skis, parasailing and also taking people snorkeling. His rates were very reasonable. He was also very respectful. We were not on any group trip just myself and my partner and he took us snorkeling and it was fantastic. Way better than the excursion we booked. Don't remember his name but he was on the beach between Club Med and the Westin. So check it out.