Calica actually has a ship dock - but that is it. Some locals set up tents in a parking lot area and there are plenty of cabs to take you to wherever - but nothing in the port itself. In fact there is some sort of mining going on in the area so it is not even pretty, but it is very close (about 15 minute drive) to Playa Del Carmen. I think it was $20 for a cab, but that was last year and I may have forgotten. You can go south to Paamul and there is great coral for snorkeling or diving. The ship tours for snorkeling go to the Scuba Mex Dive shop in Paamul, but I think you could take a cab there and save some money if there are more than 2 in your group.
Playa Del Carmen is a very nice beach, but you cannot snorkel there - too many waves, not enough coral and therefore no fish. But the little shopping area and beaches are great. It is a tender port - it does not have a ship dock. You could still take a cab to where there is coral though.
Cancun is about an hour down the road. More party atmosphere, much more built up. I've never been there on a cruise, just on a land trip.
