Banco Chinchorro (Chinchorro Bank) is by some measurements the largest coral atoll in the Northern Hemisphere and a paradise for divers and snorkelers alike. About 48 kilometers (30 miles) northeast from Xcalak , Chinchorro is a marine reserve and is known for its spectacular coral formations, massive sponges, and abundant sealife.
Scores of ships have foundered on the shallow reefs through the years, but (contrary to innumerable misreports) the wrecks cannot be dived. Not only are they protected as historical sites, most are on the eastern side of the atoll, where the surf and currents are too strong for recreational diving.
The famous 40 Cannons wreck, in about three meters (10 feet) of water on the atoll’s northwest side, is good for snorkeling but not diving, and thanks to looters there are nowhere near 40 cannons.
There are small government and fishermen’s huts on one of the three cays, Cayo Centro; as of 2010, tourists are finally permitted to stay overnight, which means spectacular multiday diving and snorkeling opportunities .