DivePartner1,
The incident I was witness to occurred because the boat's crew went around all gear and "checked" the valves. Everyone actually set their gear up. Some people turned their air on and some did not.
I personally, turn it on to check for a full tank before leaving the dock, check my primary and octo for breathing and leaks. Then I turn the air off AND BLEED THE SYSTEM. I do this for two reasons. First, if an o-ring fails or a tank falls, you don't lose a sizable portion of your air until the problem is solved. Second, I want to know that I actually turned the air on and pressurized the system predive. If I turn the tank off and don't purge the system it looks like its on. I want to start from zero and know that everything is on. I believe that boat crews also don't want a leak to suddenly occur and some may be instructed to make sure all valves are off.
Unfortunately, on this boat, some of the divers left their tanks on. When the boat crew went around turning off the valves for the run out to the dive site, the systems were not purged. Without taking a few breaths and looking at the guage, the diver who left their tank on would believe that nothing had changed.
The unlucky diver probably should have done one more check of their system pre dive but in all honesty, if they believed their system was on and their guages read a full tank, they had no reason to believe differently. They had already checked it.
Also, everybody out there...I want to see a show of hands of all those (with years of experience) who has NEVER jumped into the water with a tank turned off or forgotten their weight belt. I don't know one person it hasn't happened to for whatever reason. You can blame a failure of buddy checks or excitement to get into the water. As humans we make mistakes.
We simply don't need any assistance in our mistakes. I believe that having another set of hands on your gear--especially if you are unaware of it, is dangerous. There are three or four incidents in this one post that have had the same problem. Seems like an awful lot incidents for 20 or so replys don't you think?
Larry Stein