One thing I have learned the hard way(more than once..) is to have masks that fit properly and are WATER TESTED before you go. A couple years ago my darling wife assured me (several times) at our local dive shop that a new mask she picked out fit perfectly. Well, on vacation, out on a boat her new mask leaked badly. So did the loaner masks the operator had. Anyway, we eventually got her outfitted at the cost of two new masks and a wasted day on the water. I can’t imagine the frustration of dealing with several people in this situation, in Mexico.