What could have happened?

[sharksdelight]

Nothing to be embarrassed about. I don't know any experienced diver who has not had this happen at least once. When I was instructing, this occurred to several students who did not pay attention and fixing it for them underwater was no big problem. If the tank completely slides out of the straps, usually it will just float along side you or even be positively bouyant. I've never seen one go negative and drag someone down. I can't imagine that 2 divers took so long to retighten the straps that they drowned, even at 115 feet. It only takes a few seconds to fix things. I'm surprised that this occurred.
This is also why I prefer ScubaPro BCs, their tank clamps are just about foolproof and I have never seen a tank come loose when someone was wearing one of them. Remember also, that velcro does wear out in terms of its holding strength and if yours is so, just buy a new strap.
If a buddy is not around, like someone here said, just grab ahold of it and surface like you would on any dive.
Another thing you can do, if you have practiced in a pool and feel comfortable doing so, is simply remove the BC Underwater making sure you have a good handle on it, and keeping your reg in your mouth, you can tighten it yourself and re-don the BC. This takes some practice but it was something I used to have all my students do in the pool as part of their OW certification.
Steve

 

[Ayisha]

I can't imagine that 2 divers took so long to retighten the straps that they drowned, even at 115 feet. It only takes a few seconds to fix things. I'm surprised that this occurred.

This occurred on the Arabia in Tobermory, Ontario, which can be about 38 - 40F at 115 feet, even in the summer, can have a current, is penetratable and sometimes has poor visibility. The Arabia has claimed more than a few lives and is considered a dive for only advanced divers - not indicated by the c-card, but only divers with a lot of similar extremely cold deep dive experience. The Arabia (and Forest City) are usually by permission only. When I first did it, my log books were examined for gas management and counted for similar dives, and I was watched on the "normal" dives with the charter first, which is what most of the dive ops there do. The Arabia's reputation precedes it and many divers will get anxious diving it for the first time, and it has an eerie quality about it, which doesn't help. Until you get near the bottom of the line, you can't see much, and then it starts to appear like a ghost ship in the mist. When the conditions are perfect, you would never imagine that it could be that challenging, because it isn't that deep.

So, if someone or a buddy pair is anxious, is dealing with a problem at depth in 38F water in possibly low viz and current, the gas will be depleted very quickly. Add to that some level of narcosis, poor gas management and monitoring skills, and the issues are intensified.

I don't know what the training levels or experience were of the mother-son pair that perished, but the conditions are not the typical 115 foot dive. I recall that the accident was documented in the DAN report, but I don't remember the details.

 

[sharksdelight]

You make a good point Ayisha, narcosis and anxiety brought about by cold water and low vis could certainly have turned things into the nightmare it was. If this incident happened in warm waters, great vis and little current than I would rack it up to a low level of training and the panic that a small incident created, and panic kills.
Steve

 

[Graeme Tolton]

Most of the deaths on the above mentioned wrecks, are attributed to lack of training and experience. Trying to do simple tasks when you are near hypothermic, in 38-42 degree water while wearing a 7mm wetsuit, 7mm gloves can be very difficult. Cold water very quickly can diminish your dexterity. I can only imagine that the pair that died in the above incident, wanted to solve the problem on the bottom, rather than fight with the mooring line that is usually on about a 45 degree angle, making it a hairy ascent with equipment hanging where it shouldn't be.

 

[fjpatrum]

I'm a little late to this, but in my few dives it's not just stretch. I've seen a DM and several other more experienced (100+ dives) divers thread the strap incorrectly through the buckle. If you don't get the "cam" action from the buckle, it will come loose much more easily.

It doesn't sound like that was the issue on your tank, SoccerJeni, if you heard the thing snap back when your buddy reengaged it, but it definitely happens. After I started futsing with my BP/W it took several times to get the correct threading on the buckle and now I religiously check them every time I do anything with the strap.

 

[vladimir]

I have seen tanks slip out on a few occasions and refastened one mid-water. It seems like a pretty common problem, though I haven't seen it happen lately (maybe because lately I dive alone, for the most part, or maybe cam straps have improved). One solution, as has been observed, is to wet the strap before tightening. Unfortunately--as has also been observed--that is not always convenient, doesn't always get done, and seems to me to be "a skills solution to a gear problem." Especially if you're a new diver, you don't need more items on your pre-dive checklist. DSS rigs have rubber "tension pads" that compress upon tightening of the cam strap and expand to take up any slack in the cam strap that emerges during a dive. ScubaPro BCs also have effective cam straps, though I'm not sure why. They do have a gripping surface that the tank is held against, and they seem to tighten more than some others I have used. If your BC doesn't hold the tank effectively, get a better BC.