> No, "normal" humans don't dive to 80m deep, where the explosion occurred.
This simply isn't true, I myself after a technical advancement in my PADI to be certified on a rebreather went >80m many times. It's absolute more common than it was in the past.
Those who are trained with special forces as alleged would also be required to be qualified.
I want to clarify my answer here as I made it seem a bit more nonchalant than it is, there is definitely some technical training that needs to be done to dive deeper, as you say no recreational scuba enthusiast should just try it. There are different gasses that you need and a whole different approach to preparation and decomp.
My main point is that it's not as rare as some might think, it's becoming more and more recreational.
The people who did it definitely took on risk, but in my eyes, more so because if something did happen to go wrong, there's no support to help you out (that we know of). It's a flying with 1 engine scenario. The fact that it was pulled off is impressive. But for any rec divers, don't try without the right training, equipment and people with you.