I am a Dive instructor and did 8 months in Grand cayman working for redsail. This is the King of Dive spots. tiny island 35 plus dive operators . I have dove the great barrier reef. amazing for diversity. Cozumel is great current diving at night but Cayman islands are a must. I have touched the tip of a 14 foot hammerhead shark. Dove with 10 plus 8+ foot black tip reef sharks and dove the underwater cenotes in the yucatan peninsula about 2 hours south of cancun. Check out the pics. Freakin unbelievable. Our diving is great around vancouver . winter is best with 1 plus foot of snow on the shore as you dont have run off meaning 100 plus vis. at times. Gotta dive the 5 wrecks off the coast . Chaudier destroyer is the best !!!
but the caves in mexico rock, check the pics out...
http://www.cambsac.com/newsletter/de...0/yucatan.html
http://www.hiddenworlds.com.mx/cavern.html