The remains of German U-boat U-166 were found at the bottom of the Gulf of Mexico over 50 years after it sunk

The Type IXC U-166 joined the Kriegsmarine in March 1942, during the Second World War. After completing training with the 4th U-boat Flotilla, it was transferred to active duty with the 10th U-boat Flotilla. Its initial patrols were near the British Isles, followed by a journey to France and then across the Atlantic to the Gulf of Mexico.

During the U-boat‘s short service, U-166 sank four ships: the Dominican sailing vessel Carmen, the SS Oneida, the Gertrude FV, and the SS Robert E. Lee (1924). The destruction of the Robert E. Lee ultimately led to the U-boat’s demise.

On July 30, 1942, U-166 torpedoed the Robert E. Lee just south of the Mississippi River Delta, causing the ship to sink. Her escort, the submarine chaser PC-566, launched a counterattack. Skipper Lt. Cmdr. Herbert G. Claudius reported sinking the U-boat with depth charges, but Navy officials dismissed his claim and removed him from command. Claudius was subsequently sent to anti-submarine warfare school.

On the same day, a U.S. Coast Guard Grumman J4F-1 Widgeon spotted a U-boat near the Louisiana coast. The crew of the aircraft reported attacking the submarine and hitting it. That day, U-166 and its 52-man crew were declared missing, even though no U-boat was recovered after the assault.

The wreck of U-166 remained undiscovered until 2001, when the remains of the Robert E. Lee were found less than two miles from the attack site. Using sonar, researchers located the U-boat resting 6,650 feet underwater. Although buried in silt, its conning tower and deck gun were still visible.

Since the remains of the crew were aboard, U-166 was later recognized as a war grave.

In 2014, a survey of the submarine uncovered heavy damage to its bow, leading historians to theorize that a depth charge struck the forward deck. This explosion likely triggered U-166‘s torpedoes, causing the vessel to sink.

As a result of this new information, it was determined that PC-566 had actually been responsible for the U-boat’s loss. Claudius was posthumously awarded the Legion of Merit with Combat “V,” with then-Secretary of the Navy Ray Mabus saying, “Seventy years later, we now know that [Claudius’s] report after the action was absolutely correct. [Claudius’s ship] did sink that U-boat, and it’s never too late to set the record straight.”

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U-166 holds the distinction of being the only U-boat to have ever been lost in the Gulf of Mexico.