Mike shared a Facebook link for this video, which was floating around the different jeep groups. Here’s the youtube version.
https://www.youtube.com/watch?v=DNSoMjTJ4qY
This 1952 Video by Warner Pathe News follows the M-38 and Diamond Reo M-34 underwater. After these tests, you’d expect Willys would have sold Willys Scuba Gear.