For only $250, I'm running trips to the bottom of Lake Norman, and YOU can become a mission specialist and wear the patch proudly!
In all seriousness, I used to do a lot of scuba diving, and have even done some decompression dives. Even being at 100' to 200' below sea level is serious business. One atmospheric pressure every 33' below sea level. You'd be surprised how quick that adds up. Plan your dive, dive your plan and know your tables.
I understand being underwater in a pressurized submersible is not the same, however, the dangers of pressure underwater are the same.
I have little doubt that once that sub lost contact, it was gone that second. I read it was a planned 480 minute trip. Contact was lost about 105 minutes into the trip. The titanic lies around 12,000' below sea level. Sub had to be well below a couple of thousand feet underwater. I have no doubt actual diving limits for military subs are confidential, but in general, you won't find one that will go below 1000', and that's even pushing it. Don't get me wrong, I know smaller special built subs can and do go deeper, but at that kind of depth, it's instant game over with any small possible defect. I believe this was the 3rd decent to that depth for this sub. Just wonder what kind of testing was done on the hull after each dive.
I understand equipment "ratings" can be a political game for organizations to make money, but when you're dealing with life and death situation when using a product, I do believe their is an argument for some kind of official testing.
Bigger question is who will be paying for "search and rescue" operation? Figure how much fuel and man hours were used? Reality is you will find NOTHING of human remains. Pack it up and let what's left sit at the bottom. New "international rule" is you want to run a paid trip past 800 feet of water for people that have more money than brains, any issues, you're on your own or bill the people directly that have more money than brains.