If you're serious about snorkeling and want to dive too, then a boat sounds like a good idea. If you just want to turn up at a beach and snorkel, you can also take a boat from Palancar Beach. There's a new report on all the beaches that includes information and photos for Palancar Beach on my website today...
Hope that helps a little...
Ian
COZUMEL - returning greater than ever!
http://www.wilmacozumel.com