To be honest, any spot in Ko Phangan you choose, is probably going to be great for snorkeling. The only difference is an access - if it's hard to get there it's not going to be crowded.
WARNING: Effects of the January 2010 earthquake, political tension, and high crime have resulted in travel advisories being issued by foreign governments. Infrastructure may be damaged or inadequate, and looting, intermittent roadblocks set by armed gangs, violent crime including kidnapping, car-jacking, and assault remain commonplace. In addition, a cholera pestilence threatens Port-au-Princeas of October 2010. With the notable exception of Labadee, travelers to Haiti should remain alert and aware of their surroundings.