Cozumel is an island about 30 minutes off the coast of Mexico by boat.  We have been there twice and both times we took the ferry to the mainland so we have actually never seen the island.   The first time we went there we traveled to the Mayan ruins of Tulum, which was really interesting since it was our first ruins.

The second time we went on a underground cave walk which has been one of the coolest things we have ever done.  At points we were walking through the caves in chest high water.  You don’t know dark until you turn off the lights in an underground cave.  You could stay in there forever and your eyes would never adjust to be able to see anything.