IMHO, the best snorkeling was at CSS. Not only do you have the sunken ship and the other reefs, but the spots down by Charlie's grotto and the spa right off shore are not too bad either.
The beaches at CSA and CN aren't really snorkel-able (although you can see some sea life occasionally) and they both take you to the same reefs offshore, so the snorkeling in that respect is exactly the same.
Have a fabulous trip, no matter which you choose.
Ragnar Relay 2014 - MIAMI to KEY WEST!
Marine Corp Marathon: 10/12 4:09
NYC Marathon 11/6/11 - 4:21
Chicago Marathon 10/10/10 - 4:19
Marine Corp Marathon '09 - 4:26 / '08 - 4:28[/FONT]