Really shallow! 22 feet. That's within the range they let uncertified divers scuba at.
You probably meant "divers with a basic SCUBA certification" (open water, ~30ft depth and conditions similar to your previous dives)
12m and 20m are basic recommendations listed here. I seem to remember 30ft and 100ft (plus following tables / computers) as the recommended limits.
I have a recreational dive certificate issued by NASDS Australasia in 2000. Looks like NASDS Australasia has since faded from view, and NASDS USA joined with SSI around 1999.
It appears SSI adhere to ISO 24801[1]
1. https://en.wikipedia.org/wiki/Scuba_Schools_International#Re...
I don't get how anyone could dive for fun, it's scary down that deep :)
For anyone free diving at that depth, I'd encourage you to ensure there's always someone nearby that is capable of rescuing you.
Shallow/deep water blackout[1] is certainly dangerous with a buddy, but it's deadly if you're alone.
[1] http://divewise.org/science/physiological-causes-of-freedive...
Rescue is related. I doubt anyone could pull somebody out that's passed out at that depth. You're just not going to have enough air. I had to help someone out of a pool once and the only way I was able to manage was by walking along the bottom with them on my shoulders to shallower area. They panicked and tried to climb me, pulling me under if I did anything else
Well done helping that person. Rescuing a free diving blackout has the benefit (for the rescuer) of an unconscious victim.
Who is "they"? There is not some scuba sheriff who magically appears and stops you from going as deep as you want. Get some gear, swim out, and dive. How deep you go is 100% up to you.
Also, dive computers make the whole thing very safe by tracking exactly how long and how deep you can stay without needing any lengthy nitrogen releasing safety stops. As a recreational diver with a bit of experience, you can feel very confident going down to 160 feet (maybe even 200?) as long as you listen to your dive computer.
They're not cheap, but they're also not all that expensive.
So, if you're "uncertified" and you somehow managed to get yourself a filled air tank, then my point still stands: you can go down to however deep you want.
And the basic open water certification is not much more than a rubber stamp. Anyone can get it as long as they pay their $100 to PADI or whoever else.
You can see tables of the no decompression time: http://elearning.padi.com/company0/tools/RDP_Table%20Met.pdf
The calculations are quite confusing do to manually, but your computer does them great, and in realtime, and for your exact depth & time. So, like I said, as long as you follow your computer, the risk for nitrogen narcosis or any other problems is very very small.
But I still argue the point: the depths that you will suffer seriously from nitrogen narcosis are beyond how deep you could even go on 1 tank + no decompression time.
Once you get to 160 ft you only have a few minutes at that depth, so realistically you couldn't even go deep enough where nitrogen narcosis would be a big problem.
So I still stand by my statement: if you have only 1 tank, and follow your dive computer's guidance, your risk of anything bad happening to you on a dive is slim to none.