If your planning a trip to Mazatlan to go diving STOP, don't do it. SCUBA diving in Mazatlan is something you do when you've done everything else, twice. No really, the effort to get into the water is not justified by the sea life or the view. Plenty of star fish and clams, at few puffer fish and other small reef fish but the visability is so bad you spend most of your effort staying in contact with your buddy and the dive master. OK so it was an exceptionally poor day when we when but according to the dive master it only gets slightly better on the good days and the best days are very infrequent. Mazatlan is a wonderful place to have a family holiday, and if your going to be there for a while you might as well go for a dive, but don't bring your own equipment and don't expect much.