A PADI five-star instructor development resort at the north end of Xcalak, with rooms and a restaurant attached, which matters in a village this small — there is not much else.
Xcalak's own reef is the last Mexican stretch of the Mesoamerican barrier before Belize, protected as a national park since 2000 and about as undived as Caribbean reef gets. The fly fishing in the lagoon behind is legendary for permit and bonefish, and the operators here run that too.
XTC is also the usual departure point for Banco Chinchorro, and runs the whole PADI ladder, snorkelling and shore excursions.