SCUBA!!

[sphelps]

Diving isn't that good in the Mayan except for maybe Cosmel, I would consider Cuba, Jamaica or La Romana in Dominican for similar priced Caribbean vacations. Cuba was really good as you see some stuff there you won't see other places in the Caribbean and you'll have a lot of freedom with where you want to go and whatnot but I wouldn't recommend it unless you're pretty experienced as the dive masters will not look after you like they do other places and the equipment isn't ideal, I remember having a few leaks and running out of air but that never bothered me that much. Make sure you go somewhere with a dive shop on site, my best diving experience in the Caribbean so far was at the Dreams in La Romana.