Several groups gather at the Aqua World site for several different functions, which can be kind of confusing. You get a free breakfast of fruits, drinks, cereal, etc. Then your group loads onto the boat to ride over to Isla Mujeres, about a half-hour trip with free drinks. We arrive at the island and lounge at the beach for about an hour and a half, then have lunch at a big buffet (included in price). After that, we get on the boat to go to another area of the island to learn to snorkel. They teach you the basics, break into small groups, and take you out to snorkel for a good while. I'm not sure exactly how long it takes, but they timed it perfect, because you see a lot, but don't get totally worn out or bored. It's beautiful and very fun.
Then, back to the boat, you have free drinks and a cruise to another side of the island, where you can wander around the little town and shop for many nice souvenirs, many at better prices than similar stuff in Cancun. Be ready to haggle for prices; they enjoy it. Then it’s back to the boat for several free drinks on your way back to Cancun.
As fun and scenic and exciting as the whole trip was, the best part of all was the crew on our boat, especially our snorkel teacher, Hector, and Frankie, one of the funniest people I've ever met. Do this trip if you go to Cancun! It was the highlight of our whole week.