>>287358SCUBA didn't exist in WWII. If you were on compressed air, you were on an umbilical.
Rebreathers were the only way to offer a man-portable system.
Simply put, it was easier to just use pure oxygen:
1.) With pure oxygen, 0-30 ft, you have unlimited dive time.
2.) You will consume very little oxygen compared to your sodalime scrubber (which you will burn out quickly), so only about 10cf is needed.
3.) With CCCR units, no pressurized oxygen was needed. A chemical cocktail produced oxygen. The downside is that mixing it with water would kill you, so you had to NEVER spit out your mouthpiece.
There were a couple systems that used nitrox (higher O2 percentage than air), but they were not as popular due to their complexity, plus gas mixing was required.
Compressed air doesn't work for rebreathers, since you only consume the oxygen. You'd end up wasting a lot of gas refreshing the loop. It'd have to purge a lot of air in to the loop to get the PPO2 back up to a usable level...the whole time, the system would be bubbling away, which defeats the purpose of a military rebreather.
