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

USS Robinson (DD-562) firing its 40mm guns to cover UDT men clearing beach obstacles for the 1st Marine Division at Peleliu in September 1944. Courtesy of Naval History and Heritage Command.

When the war broke out on 25 June 1950, a 10-man UDT detachment led by Lt. (jg) George Atcheson was in Japan making beach surveys and assisting Marine Corps personnel in training Army regimental combat teams in reconnaissance techniques.

Underwater Demolition Teams were the answer found during World War II to the problem which led to heavy Marine Corps losses in the invasion of Tarawa in the Pacific in 1943, and which faced the Allied Expeditionary Force before the invasion of Normandy in 1944.

2025年3月11日 · Then, there were no Navy SEALs but rather the frogmen of America’s Underwater Demolition Teams (UDTs). When the Japanese attacks on Pearl Harbor and the Pacific pulled America into the chaos of World War II, the U.S. Navy and Marine Corps didn’t have a dedicated beach-clearing and reconnaissance unit.

Midmorning on June 14, 1944, UDT-5’s “frogmen” slipped into the water off Red and Green Beaches, designated landing zones for the 2nd Marine Division’s amphibious assault the next day. With a barrage of naval gunfire shrieking over their heads, the swimmers got to work.

UDTs were pioneers in underwater demolition, closed-circuit diving, combat swimming, riverine warfare and midget submarine (dry and wet submersible) operations. They later were tasked with ensuring recovery of space capsules and astronauts after splash down in the Mercury, Gemini and Apollo space flight programs.

2018年9月17日 · UDTs were tasked with completing full sweeps of the beaches and waters off an island's coast. The purpose of these missions was to determine if there was anything, man-made or naturally-occurring, that would impede the arrival of landing craft. If they encountered any underwater obstacles, it was their task to demolish them.

2023年6月2日 · Key Takeaway: During the Korean War, Navy SEALs’ predecessors known as Underwater Demolition Teams (UDT) played a crucial role in the Inchon Landing and Rescue Operations. They acted as wave-guides for Marines during their amphibious assault on Wonsan Harbor, cleared paths through mine-infested waters for Marine Corps landing craft, and ...

2023年9月11日 · What is the history of UDT? The Underwater Demolition Teams (UDT) originated during World War II to clear beach obstacles for amphibious landings. They pioneered combat swimming and played crucial roles in many significant battles.