After we finally collected the requisite number of people, we were herded into a taxi and driven to the helmet death (more on this name soon) diving area, which was sort-of a part of a local restaurant. The key information were were given is that Carlos was responsible for getting us back to the ship via another taxi after out diving-we were given the option of doing some snorkeling by ourselves after the helmet death/diving if we wanted to, though no one on our group took advantage of this. A few people from an earlier group did hang around and snorkeled. We waited in the restaurant/jewelry store (yes, also seemingly part of the establishment, as was a guy selling cigars) and were given a talk (read sales pitch), not on helmet diving/death, but on making black pearls, by the owner of the jewelry store attached to the diving/cigar/restaurant establishment.
After being given a locker key, we shed out clothes and were given instruction on how to helmet dive. This consists of a 70 pound steel helmet with a large face shield and an attachment for an airline. To use it, you go down a ladder into the water, they lower the helmet onto your shoulders, and you finish your descent down the ladder to the bottom. The main thing to remember is that you MUST stay perfectly upright, as the helmet just rests on your shoulders, and is the only thing holding you down. If you tip your head forward, water can get into your mouth or nose.
At this point, once all of us were on the bottom, we held onto a rope and walked single file in a square around the area. There is a part of a small airplane, plus lots of fish (they are fed during part of the tour, so they hang around).
This is when the death part came in. My airline came undone. The helmet, which is quite noisy from the rushing air, was suddenly very, very quiet. Too quiet. After 2-3 more breaths, it became apparent that I was getting no more air, but the bubbles from others said they were still getting air. As I was the last one in line, no of the other participants could see my predicament. I tried to signal to the safety divers (we were trained on how to do that), but they did not see me at first, so I turned around and started walking back to the ladder. The safety diver suddenly spotted me, and quickly came over and asked (by hand signal) if I was OK. I signaled back no, and they suddenly realized that my airline had come off. They used the backup regulator on their SCUBA gear to give me air while they found and reconnected the airline. Everything after that was fine, and I finished the tour, but for about 20 seconds, it WAS interesting. (In my youth I was a Red Cross and Boy Scout trained life guard, and if I had not gotten help in a few more seconds, knew that I could have dropped the helmet and shot up to the surface and been OK.) The ironic thing is that my wife is a certified SCUBA diver (I am not because of inner ear problems-though I had no problem at the 20 feet or so we went down with the helmets) and we had been joking that it should have been called helmet death not helmet diving.
By the way, despite the problems, I would do this again.
My wife went on a SCUBA expedition and had a great time.
My reason for a rating of 3 is that Cozumel is not really Mexico, but simply a tourist trap. If you provided guides in Spanish, it could have been in any ocean front country in the world.