"A group of foreign divers exploring the area..."
I guess all the Mexican divers are in the USA.
"I guess all the Mexican divers are in the USA."
Doing the diving Americans won't do.
Seriously, American cave divers are very active in Mexico. The Yucatan is underlain by a most remarkable aquifer that explorers are systematically documenting. Some groups are using cutting edge (civilian) rebreathers and spending up to 18-hours underground and underwater. There are Mayan artifacts and ancient animal bones to find. It is all very exciting if one enjoys that kind of thing.