[Navy6064]

The Underwater Demolition Teams were a newly formed unit. They were designed to chart beaches and pave the way for amphibious landings. Training for the swimmers was vigorous. The men were made to swim miles in jellyfish infested waters. Often men would have to be pulled out of the water, from being stung so many times, because they could no longer swim. All of this training was an attempt to form men who would go anywhere and would feel no pain. Men who would compete the mission, no matter what the cost.



Tasks

Underwater Demolition Teams were responsible for performing the following tasks: "hydrographic reconnaissance, beach clearance, and the demolition of underwater obstacles" (Stubblefield and Halberstadt, p. 99). All of these missions were very important because they were all necessary in order to prepare for an amphibious landing. They helped to pave the way for the landing of Marines on Normandy shore (D-Day).

HYDROGRAPHIC RECONNAISSANCE

The first of these tasks is hydrographic reconnaissance. The purpose of the hydrographic reconnaissance mission is to find out what the beach is like. These missions can be carried out by anywhere from 2 swimmers to 50 swimmers depending on the size of the beach and the amount of information needed. When searching for underwater obstacles, anywhere from 25 to 50 swimmers were used. The swimmers are dropped off far out to sea and swim in to between 25 and 50 yards off shore. Then they assemble a line parallel to the shore. Once in line, the swimmers begin searching for underwater obstacles. They do this by diving down and swimming in a zigzag pattern. By swimming in a zigzag pattern, the swimmers are able to maximize the amount of area they cover searching for obstacles. (See diagram below)



Other purposes of the hydrographic reconnaissance mission were to take samples of the sand on the beach. These on-the-beach missions were usually carried out by one or two swimmers. The fewer swimmers out of the water the better, because it is very easy to detect the swimmers on the beach, however, it is difficult to detect the swimmers in the water because only their heads are showing. The beach is analyzed to see what type of support it will give to heavy equipment. It is difficult for tanks and heavy troop carriers to move if the sand is too soft. While taking these samples, the swimmers also look to see what type of defenses are located on the beach, if there are sentries and if there are any visible obstacles or mines on the beach. Once the swimmers are done with the on-the-beach reconnaissance, they quietly slip back into the water and swim out to sea where they are joined by the rest of the team and are picked up by a waiting ship.

BEACH CLEARING

Once this task is done, the next mission is to clear the beach obstacles that are in the way, so the amphibious landing can take place. The next night, the swimmers return to the beach with explosives. They place their charges (ranging from TNT to explosive hose) around the obstacles and then tie all the charges into a single detonator (commonly called a "hell box"). The swimmers then swim out to sea and detonate the charges.

UNDERWATER OBSTACLE CLEARING

Underwater obstacle clearing is done at the same time that beach obstacles are cleared. Underwater obstacles are cleared by placing waterproof charges around the obstacles. All of the charges are then tied into a single detonation cord, which ties further into a detonator. The swimmers then swim out to sea and the charges are detonated, clearing the obstacles. Usually, the beach charges and the underwater charges are placed and detonated at the same time, that way the swimmers only have to go close to the shore once under the reasoning that the closer to shore you are, the more dangerous it is, because it is easier for the enemy to see you.

DIVERSIONS

Sometimes it was necessary to make the enemy think that a certain beach was going to be attacked, when in fact, it wasn't. This tactic is called a diversion. UDT's would perform this tactic by swimming up to a beach that was not going to be used for an amphibious assault. They would then begin a "recon" (reconnaissance) of the beach and the area around it, making it obvious that they were there. This way the enemy would know that something was going on. Next, they would place demolitions on the beach and on obstacles (if there were any) in the water. They would then swim out to sea and set off the charges. By doing this, the enemy would think that something is going on out there, and therefore, the beach they are guarding is going to be used for an amphibious landing. The enemy will call for reinforcements, which will divert defenses from other beaches that are going to be used for the actual assault. This type of diversion mission was done at the same time that hydrographic reconnaissance missions were being conducted at the beach to be used for the landing. Therefore, two teams were needed; one for the diversions, and one for the actual reconnaissance. The diversion mission is extremely important because if it is not successful, then the other hydrographic reconnaissance mission will have been in vain.



Equipment

Underwater Demolition Teams used different types of equipment to accomplish their missions. The first combat swimmers had little swim equipment. Often they would plunge into the ocean with little more than a pair of canvas swim trunks. Masks, breathing systems and cold water suits were not yet being used by the Navy (Stubblefield and Halberstadt, p. 99). These early combat swimmers usually had no more than a knife attached to their belt for protection. However, when the UDT's knew that they would be going into a dangerous situation, they could ask for gunfire from Naval Destroyers. These Destroyers were extremely accurate and were able to suppress most of the enemy fire the UDT's were facing on the beach. The shelling was extremely successful for getting rid of snipers located on the beach.