We snorkeled at Punta Sur in March 2010. It's a bit of a swim out to the reef from the beach, but there are platforms to rest on if needed and it's worth the trouble once you are there. Probably best for intermediate to advanced snorkelers. Long coral reef with lots of sea fans, plenty of fish and coral etc. Also saw a nurse shark, some large rays and a turtle. There were only a few other snorkelers out there and the reef is quite large so we felt like we were on your own. Punta Sur is a protected park area at the south end of the island. The best way to get there is by taxi, but you have to arrange for a pick up with the same driver who takes you there (something they are accustomed to doing). Decent washroom facilities and a small stand for drinks and food.