Banco Chinchorro is the big prize for serious divers and snorkellers based in Xcalak. The offshore reef reserve is far enough out to feel like an expedition, with coral, clear water, wreck history, seabirds, and crocodiles in the wider atoll environment.
Access depends on weather and authorised operators, so do not build a one-day plan around it unless you have confirmed the trip. When it works, it is one of the strongest marine experiences on the southern Mexican Caribbean.