Underwater Demolition Team.

The competitive squads of the [UD] platoon. Hooah!

The Underwater Demolition Teams (UDT) were an elite special-purpose force established by the United States Navy during World War II. They also served during the Korean War and the Vietnam War. Their primary function was to reconnoiter and destroy enemy defensive obstacles on beaches prior to amphibious landings.

The UDTs reconnoitered beaches and the waters just offshore, locating reefs, rocks, and shoals that would interfere with landing craft. They also used explosives to demolish underwater obstacles planted by the enemy. As the U.S. Navy's elite combat swimmers, they were employed to breach the cables and nets protecting enemy harbors, plant limpet mines on enemy ships, and locate and mark mines for clearing by minesweepers. They also conducted river surveys and foreign military training.

The UDTs pioneered combat swimming, closed-circuit diving, underwater demolitions, and midget submarine (dry and wet submersible) operations. They were the precursor to the present-day United States Navy SEALs.
In 1983, after additional SEAL training, the UDTs were re-designated as SEAL Teams or Swimmer Delivery Vehicle Teams (SDVTs). SDVTs have since been re-designated SEAL Delivery Vehicle Teams.

Active: 15 August 1942 – 1 January 1983

Country: United States of America

Branch: United States Navy

Type: Amphibious warfare

Role Primary tasks:
Underwater demolition
Reconnaissance
Infiltrating and exfiltrating by sea

Garrison/HQ: Fort Pierce, Florida, Maui

Nickname: UDT

Engagements:
Operation Overlord
Korean War
Battle of Iwo Jima
Battle of Okinawa
Operation Torch
Borneo campaign (1945)
Battle of Peleliu
Battle of Saipan
Battle of Tinian
Battle of Guam
Battle of Leyte
Invasion of Lingayen Gulf