Best Of These Options? Need Opinions Please :)

[amocksun]

Hello all! Last year we went on our first cruise and snorkeled in Cozumel and Key Largo (we drove there after) and we just went on our own, right off the beach. We regret not taking a boat out to a real reef and snorkeling. Now, we're looking at going again in October and we're taking our 8 year old who really wants to snorkel and see some colorful coral and fishies. So, the ports we're looking at are: Key West, Cozumel, Nassau, Freeport and Half Moon Cay (Carnival's private isle). Any opinions about where the best snorkeling is out of those places would be greatly appreciated!