If you're looking for some fun in Cozumel away from the beach, check out Wild Tours Xrails. Aquatic activities are my absolute favorite thing to do in a destination with such blue waters and perfect weather, but every now and then the beating hot sun becomes a little too much.
If you aren't afraid to get a little dirty, you will have an amazing time driving down dirt roads on a xrail vehicle. They are a mix between an extreme go-cart and an ATV with the capability to go over and through just about anything. During the drive we stopped to see ruins as the guides spoke about the ancient civilization, and then continued onto the cavern.
Once at the Jade Cavern you can swim in the water, or jump in from the top of the cave. The water appeared to be dirty but the guides explained to us that it was actually really clean. Bats dwell in the roof of the cave, but I never saw one fly around. The excursion itself was a lot of fun and well orchestrated. I highly recommend this activity for you trip to Cozumel. You wont be disappointed!