Yes, they provide you with a snorkel mask but it doesn't matter because you can not see ONE thing in the water. They do not go out far for you to snorkel so you are basically next to a break wall where there is zero visibility. The water is a murky green and there doesn't seem to be any sea life. They also only allow you to swim in front of the boat and you can only JUMP off the boat, you can not dive. The main attraction of this trip is a mat and a water trampoline (which you can't really jump on, you basically fall). I didn't even want to swim in the water because it was so murky. DO NOT GO ON THIS TRIP IF YOU WANT TO SNORKEL.
If you don't want to snorkel then it's a lovely ride, the captain and crew were nice and not annoying. They didn't try to "entertain" the passengers with silly lip syncing routines or crude jokes. Some of the people appeared to really enjoy the trampoline and mat, some just stayed on the boat.
Bring your own food, they provide water, soda. You can buy beer and wine for $3.
If you want to pay $55 for a nice boat ride then go for it, I was told the best snorkeling is in the keys which I intend to visit next time.