Underwater Demolition Team 4"

Underwater Demolition Teams (UDT), or frogmen, were amphibious units created by the United States Navy during World War II with specialized non-tactical missions. They were predecessors of the navy's current SEAL teams.

Their primary WWII function began with reconnaissance and underwater demolition of natural or man-made obstacles obstructing amphibious landings. Postwar they transitioned to scuba gear changing their capabilities. With that they came to be considered more elite and tactical during the Korean and Vietnam Wars. UDTs were pioneers in underwater demolition, closed-circuit diving, combat swimming, and midget submarine (dry and wet submersible) operations.