Update: I ended up going to Los Arcos with Pacific Scuba, apparently they went to the Marietas the day before and the viz was pretty poor. Rental gear was in pretty decent condition save for the chewed up mouthpiece in the reg which fell apart on the boat (second time that has happened to me with rentals). They swapped it out with a spare reg and away we went. When we arrived to the site, there were 3 other boats already there with only a handful of divers each.
Overall I found it an interesting dive though my expectations were somewhat reserved from reading various posts here.
First 40-50 feet was like diving in bathwater, lovely and warm then we saw the thermocline shimmering ahead of us, once we passed through the viz was better but boy was it chilly. We dropped down to approx. 80ft then went along the canyon with the wall on our left, it was pretty cool hovering over that dark abyss below. Second dive was further along went to about 60ft, saw the biggest moray I have ever seen in my life, in fact nothing has come close to the monster we saw. Maybe he's a well known resident there but it was cool, we tried enticing an octopus out of his hole to no avail, saw the usual angelfish, parrotfish, sergeant majors, etc. The 2 dives surpassed my expectations and I would not hesitate recommending people explore PV. It seems like the caribbean divers on the cozumel side always diss PV, having dived in the philippines, thailand & tahiti I still enjoyed diving here, it beat the socks off florida in my opinion.
Pacific Scuba/Vallarta Undesea was very professional, thorough briefing and dive plan, not to mention friendly.
One interesting observation on the big cattle boats with the snorkellers that arrived during our surface interval. There must have been 50+ people scattered over the area, some of them had those floaties on with no fins, they couldn't swim and were a couple hundred yards from their boat. One guy was so tired he came to our boat to rest for a while. I can't believe how irresponsible some people can be, not to mention the cattle boat operators that take them out and dump them overboard to their own devices.
