We are looking at Chaak Tun in Cozumel (RCC Excursion) called Underground Mayan River Cenote and Famous 5th Ave shopping & Beach. Has anyone done this? My three adult kids (ages 20, 22, 25) really want to do some cave snorkeling. We are on Allure March 3rd (Nassau, Cozumel, Roatan, Costa Maya). I think my husband and I will skip it but wanted advise from people who have been on it.