Diving gear

I believe you are correct. I got the following from a Wiki article about another WWII movie, "The Frogmen," in which Navy UDT men were incorrectly depicted as using diving tanks:

Errata
In the last operation (destruction of a Japanese submarine pen), the frogmen correctly wear drysuits, but they were shown using open-circuit aqualungs, but actually they would have used rebreathers to prevent detection on the surface from streams of exhaled bubbles. That use of aqualungs is an anachronistic (see Timeline of underwater technology#1943), since the Cousteau aqualung was unknown (except to a few men in France) until after World War II. According to the official history of Naval Special Warfare[1], on October 21, 1950, "William Giannotti conducted the first U.S. combat operation using an 'aqualung' when he dove on the USS Pledge."

Rebreathers would not have been used by UDT operators at anytime during WW2. The Frogmen did not acquire any type of SCUBA gear until after the 2nd World War. The OSS Maritime Units did have Lambertsen rigs which were an early type of rebreather. The UDT operators relied on their ability to breath hold. [2]





You understand, Captain, that this mission does not exist, nor will it ever exist… — Apocalypse Now

http://jacquescousteauaqua.weebly.com/invention-the-aqua-lung.htm ... supports your point that Braden wouldn't have been running around with an aqualung then and I agree that he should have blackened his face. It even stood out in the movie.🐭

The “Aqua-Lung" was invented in 1942 and registered by the French in 1943. The US Navy UDT, as now would have access to the most advanced and best equipment available, even if still being tested. I believe the equipment used in the movie to be true to the period.