What's the deal?
Drop into a watery subterranean underworld and navigate narrow passageways in scuba gear.
Where's it at?
Once an ancient coral reef, the porous limestone bedrock of Mexico's Yucatan Peninsula contains about 3,000 freshwater sinkholes, or cenotes. Many make excellent dive sites. The water is always calm and clear and there's no chance of getting seasick on the way there.
Base yourself in tiny Tulum, two hours south of Cancun. Two of the best are Gran Cenote and Dos Ojos Cenote, two large sinkholes connected by a 400-metre channel. Follow your divemaster from faintly lit grottos into inky inner chambers, flick on your dive light and illuminate alabaster and dirty-brown stalactites, hanging from the ceiling like broken icicles and bulbous breasts.
Some of the largest underwater caves in the world are found in this part of the Yucatan, including the Ox Bel Ha system, which is believed to contain more than 180 kilometres of passageways. But don't go off exploring them on your own; many have died doing so. For those wishing to go further, specialized cave-diving courses are available through Cenote Dive Center.
Who's it for?
Those who have no fear of water, the dark or confined spaces.
Special to The Globe and Mail