The first year we went my wife and I bought mask and snorkel sets off Amazon, some nice water shoes from REI, and some inflatable pool noodles. Last year we bought some short fins and I feel like it improved the experience. We snorkeled on the cliffs and there was little to no current. I felt safe without fins but if you were out in the open water it could be a problem. I wouldn't rely on the equipment available on the boats. Or maybe buy your own mask and snorkel and use their fins. We were fine with the fins we got from Amazon but going to a dive shop would be even better. I just didn't want to drive 30 minutes each way to the closest dive shop.