Originally Posted by
NutLoose
I understand that, but they were a straight up to the surface job by, surely a full sub Aqua set up would allow greater freedom of escape.
No it wouldn't. The crew in a submarine are breathing air at 1 atmosphere. The water pressure outside the submarine is 1+(x/10) atm where x is depth in m. So if donning escape breathing gear, an escapee has to be pressurised in a water-lock in a short period of time to outside pressure, then be released to swim free. That is already quite a challenge, even just down to shallow depths. Then there is then the question of what gas they would breathe. Air is only good down to about 40-50m. Most people get gas narcosis (like being drunk) at deeper than 40m, and below 60m the risk of CNS poisoning due to high oxygen partial pressure becomes impossible to manage. Hence the RN SETT tank is only 30m deep because that is the maximum depth escape is realistically possible using air as a breathing gas. From that depth you don't need the bulk and complication of scuba gear - just swim free with the submarine escape apparatus.
Worth pointing out also that SETT training in RN is carried out in warm (above 30 degree) water with good visibility - not conditions which would normally be encountered.