We did the Xel-Ha snorkeling/river tubing trip. It was quite a ways from the Cozumel port-had to take a 40 minute Ferry ride(bring the Dramamine for that!) then walk through the streets a little to a taxi that took you the rest of the way there. The transfers were seamless and our guide Juan was perfect. He even told us to use our snorkel flippers for paddles while on our tubes. You could easily spend a few days at this park, but we only had time for a short slow tube ride down the river, some zip lining into the river, and snorkeling back to where the restaurants are for an all inclusive authentic Mexican lunch. The fish were gorgeous, although I didn't get to snorkel that much because my 6 year old was crying most of the time. (I think he was overtired and wary about the river water-solely because it wasn't a pool)
We hopped off the boat nice and early and went straight for the double kayaks with our kids. We paddled around for half and hour near the cruise boat, it was really fun. We didn't tell the kids till we were back on shore that we were paddling past small sharks! We skipped the sting ray experience, although that looked cool as well, and we saw a rope course over the water and Pelican's Plunge-a neat water slide into the water. After a little snorkeling and swimming we checked our kids into kids club on the island(finally, no computers!) and my husband and I just about ran to Serenity Bay-just for adults. We threw our rafts in the water, plopped down, and floated down the beach-absolutely the best part of my vacation. We went parasailing out of 'Marges Barges' right off the back of a power boat. The view was beautiful and the sailing smooth and comfortable(no pinching harnesses). The only drawback was the $. It was literally almost $10 a minute! And then they asked for a tip!