I just returned from a cruise this morning on the Elation, which stopped in HMC. Basically to answer your questions:
1. Are there places on the beach where you could rent a sailboat or catamaran without booking thru Carnival?
No. Although there are places to rent a sailboat or catamaan, you must realize that they are all owned by Carnival/Holland America, so you must book them through the cruiseline. Whether you book on the carnival website or wait until you get on the ship or even wait until you get on the island, is your choice, but the only way that you will do either of these will be to give money to carnival to do so.
2. Are there places to buy food?
none that I saw. They bring a buffet of food over at 11:45 and it stays up for a few hours and you can eat with everyone else. The lines are long, the selection of food is not as good as on the ship, but it is "free."
3. If we have our own snorkel gear; are there good areas on the 65 acre site or is it best to book an excursion.
It was too cold for me to go in the water, but some people were snorkeling in the beach area and reporting seeing fish, but nothing that I would have considered worthwhile. I have heard that there is some decent snorkeling right off the beach someplace on the NORTH side of the island, but I did not do it myself.
I would probably pay the moeny and go with a tour. Actually, I would suggest spanding the money and doing the snorkeling excurison that is available in Grand Turk rather than HMC if you can, because it sounded much better than what was available in HMC.
