(since the shot looked pretty ok in b&w I decided to do a mono version too for those who like the format) This is one of the boats that amateur divers can take out to the coral reef (the second longest in the world after Australia's Great Barrier Reef). I dont do scuba myself but I did do a lot of snorkelling, both along the reef and in several freshwater cenotes. A cenote is a deep pool created in places where the ground has collapsed into an underground river. The whole of the Northern part of Mexico's Yucatan peninsula, which is mostly flat, consists of one huge limestone slab. There are no rivers on the surface but plenty underground, caused by heavy rains during the wet season seeping through the porous rock. In places the roots of large trees have penetrated down to these rivers and eventually over the centuries caused the ground to collapse here and there, creating a whole series of cenotes all across the peninsula and all linked by the underground rivers which eventually flow into the ocean. The cenotes can be anything from just a few metres to hundreds of metres deep. And the rock formations you see below the surface are incredibly fascinating. Plenty of aquatic wildlife down there too.