See inside a sunken Nazi-era U-boat found in the Gulf of Mexico

The U-166, which sits nearly a mile below the Gulf of Mexico, just off the Texas coast, was sunk by Allied forces during WWII. It was discovered decades later. The U-166, which sits nearly a mile below the Gulf of Mexico, just off the Texas coast, was sunk by Allied forces during WWII. It was discovered decades later. Photo: OET/NautilusLive Photo: OET/NautilusLive Image 1 of / 23 Caption Close See inside a sunken Nazi-era U-boat found in the Gulf of Mexico 1 / 23 Back to Gallery

During WWII, the Gulf of Mexico was home to a frightening covert menace: numerous German U-boats that patrolled the southeast Texas coast.

Over the decades, these sunken vessels have been found in the Gulf's waters. These serve as reminders of just how close this state came to being attacked and potentially changed forever in the early 1940s. >>>Take a tour of the U-166, which was sunk by Allied forces during WWII, in the photos above.

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"Research suggests there were more than 20 different U-boats operating in the Gulf in 1942 and 1943," the Texas Historical Commission explains. The enemy submarines posed such a danger to the coast that cities such as Galveston, Sabine Pass, Port Arthur and Beaumont reportedly instituted "blackouts to reduce the cities' visibility" to the enemy boats.

"Their primary mission was to sink ships departing from ports in Texas and Louisiana, disrupting oil shipments and impeding the flow of military hardware and supplies to the European front," the THC reports. "Oil was critical to the allied forces in Europe and the Pacific, and the ports of Galveston, Houston and New Orleans were some of the busiest oil-exporting terminals in the United States."

The threat of U-boat activity in the Gulf was so feared that some south Texas residents said "there are so many German U-boats in the Gulf, it's a wonder they don't torpedo each other," historical writer Logan Hawks said.

The remnants of those vessels can be seen today, thanks to the efforts and technology of institutes such as the Ocean Exploration Trust, a foundation created in 2008 by revered oceanographer and explorer Dr. Robert Ballard. Its mission is to educate the public on pure-ocean facts and history through ongoing discovery voyages.

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The OET has documented a number of unearthed sunken ships on the ocean floor.

Among those is the 1941 German submarine U-166, which was sunk by Allied forces. Its wreckage was discovered on June 10, 2001, "nearly a mile below the Gulf surface."

The OET's most recent mission embarked on a new expedition in May. This year's OET trip, in partnership with the National Oceanic and Atmospheric Administration, is aboard the E/V Nautilus to explore offshore California, Oregon, American Samoa, and remote Pacific U.S. Territorial Islands.

Those interested in following along can visit NautilusLive.org, a 24-hour portal tracking the oceanographers' discoveries in real time.

Editor's note: An earlier version of this story mistakenly quoted another source saying the U-166 discovery was made near the southeast Texas coast. It should have said, "in the Gulf of Mexico."

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