Made in 1957, this amazing U.S. Navy film showcases the pre-cursors to the SEALs and the UDTs (or Underwater Demolition Teams). Underwater Demolition Teams (UDT) conducted beach reconnaissance, cable and net cutting, explosive destruction of underwater obstacles for amphibious landings, limpet mine attacks, submarine operations, and the locating and marking of mines for minesweepers. They also conducted river surveys and foreign military training. While doing this, the UDTs pioneered combat swimming, closed-circuit diving, underwater demolitions, and midget submarine (dry and wet submersible) operations. Many of these capabilities are shown in this film, which likely inspired Hollywood to create “Sea Hunt” and might have been fodder for Ian Fleming as well. An especially interesting segment shows UDTs deploying from a submerged GUPPY-class submarine, a strategy they famously employed during the Korean War to raid enemy railways.
It still blows my mind that underwater welding is not a contradiction in terms. Demolition underwater would also have its own complications. These guys probably had to do their demolition projects the old fashioned way. http://www.mcmservices.com.au/expertise/demolition