Casa Cenote

Fresh water sits on top of salt water here, and the boundary between them — the halocline — is visible as a shimmering, oily blur you swim through. Above it, freshwater fish. Below it, small ocean species that came up the channel.

Nothing about this dive is overhead or committing. It is shallow, bright, and slow, which makes it the best cenote for a nervous first-timer, a rusty diver, or a family where some people snorkel while others dive.

A saltwater crocodile has lived in the channel for years. Guides know where he rests and give him room. He has never been a problem, and seeing him is the highlight of many people's trip.