Originally Posted by
Trim Stab
They could ascend from 75m on open-circuit air, but it would be dangerous. The pp02 would be about 1.8 which is at high end of tolerance, but they would only be subject to high levels for a short period during initial ascent. They would not need any decompression stops as they would only be at 75m for a minute or two before leaving the water-lock. They could ascend with some form of collapsible or inflatable boat. I should disclose that I am an experienced technical diver, certified down to 90m on trimix open-circuit, and 80m on rebreathers.
Our SBS use Divex rebreathers with oxygen for shallow operations (<6m) and nitrox for down to about 24m. The RN FDU clearance divers use Divex rebreathers down to 80m using helium as diluent.
Sir, you have my total respect as a recreational diver but I do think happily that people who operate at those depths are slightly if not completely mad. having met a fleet clearence diver, fantasic guy and in the water he was amazing, just so comfortable.
Two questions though, a) would they have the correct gases available and b) does the boat have a lock out chamber which being the type it is I would think not. Don't the submarines normally come to just on the surface allowing the decks to wash to let SF teams out or like the USN use SDS equipment.