Jet Ski and Snorkle?

On our last cruise a couple was telling us about an excursion they did that involved Jet Ski's and snorkeling. I think it was Cozumel (the other port was Key West). I am not sure if it was through the ship or on their own (this was Carnival). Has anyone heard of anything like this available in Cozumel?

Thanks for your help. Sorry for the vagueness of my post.

You can taxi to the Money Bar, with good snorkeling from the shore. After an hour or two there (and some great nachos!) grab another taxi to Paradise Beach where you can arrange for a jet ski.

Easy! ;)