The Cenotes (truly significance sinkholes) of the Yucatan promontory are spotted only south of the occasion resort favourite Cancun. The whole Yucatan landmass was before a reef underneath the sea, then the water retreated creating the ocean life to be fossilised into the dividers of profound openings. This framed a gigantic underground universe of substantial natural hollows, karst tunnels and sink gaps some even up to several feet profound. The region is truly famous for swimming, snorkelling and encountered jumping.