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  • Stephen O. Sears

The Discovery of German U-Boat U-166 in the Gulf of Mexico

Updated: Dec 31, 2019

The German U-Boat U-166 was sunk by a US Navy patrol boat in 1942. The Navy thought at the time that the U-Boat had escaped, and its whereabouts was unknown until it was discovered by a Remote Operated Vehicle (ROV) deployed from an oilfield vessel in 2001. I was fortunate to have participated in the discovery voyage, and this is the story of finding the sunken German submarine.


I was the Shell Deepwater Development manager in 2001, and we were installing a new project in 5000 feet of water south of the Mississippi Delta. It was a record setting technological outstep in a number of ways. The water depths are over one mile deep, and the concept of a floating central production platform with several fields linked to it was a novel concept at the time. The name of the project, Nakika, came from the Polynesian Octopus God. The production platform is at the center like the head of an octopus, with tentacles reaching out to the subsea fields. One of the steps necessary to complete the project was to install a pipeline from the floating platform to shore.


Prior to laying the pipeline, a sidescan sonar survey was conducted to determine the location of any shipwrecks or other hazards on the seafloor. This is conducted by towing a “fish” on a cable near the seafloor and imaging the bottom with a sonar ping. The work was proceeding routinely, until one morning when an engineer came into my office with an excited look on his face.


“We found a shipwreck in the pipeline route that we didn’t expect.” he said.


“What do we think it is?” I asked.


“The contractor thinks it’s a submarine. We’re meeting in the conference room to take a look.” he replied.


The team had already been discussing the find when I got to the conference room, looking at the image shown below.


Sidescan sonar image of the U-166
Sidescan sonar image of the U-166

“What do we know about it?” I asked. The image certainly resembled a submarine, with the conning tower rising above the deck.


“We think it’s a German U-Boat.” someone said. There were two known wrecks on the seafloor nearby that had been sunk by U-Boats, the Alcoa Puritan and the Robert E Lee. They had been located in the 1980s by a sonar survey. The submarine that sank the Robert E Lee, the U-166, was thought to have escaped. But maybe it had not.


ROV used to photograph U-166 wreckage
ROV used to photograph U-166 wreckage

The subject of the meeting quickly changed from what to do about the pipeline to following up on a historic find. Shell had a vessel under contract (the Gary Chouest) that carried a small remotely operated submarine (ROV) with the capability to descend to the suspected submarine and send back video of what was observed. After a few days of meeting with the federal Mineral Management Service, our partner BP, and the contractor who had conducted the sonar survey (C&C Technologies), we planned a trip to the location of the submarine. On board was a film crew (these photos are screen shots from video taken that day) to record the findings and two marine archaeologists. Leaving from the port of Fourchon in Louisiana, we reached the site of the shipwreck by late afternoon and deployed the ROV.


The conning tower of U-166
The conning tower of U-166

We gathered around the screen, and watched the images as the cage containing the ROV descended. After being lowered more than one mile below the surface of the Gulf of Mexico, the ROV was maneuvered from the cage and began to send back video of what the cameras observed. The conning tower of a submarine quickly materialized on the screen. We were the first people to observe the U-166 in 59 years. Other images of the hull and a deck gun became visible.


View of the deck gun on the U-166
View of the deck gun on the U-166

If you are a scuba diver and used to seeing shipwrecks in shallower water, exposed to sunlight and higher water temperatures, you might be surprised by the relative lack of marine growth on the U-Boat. The water temperature is close to freezing year round, and the water depths eliminate the light needed by most organisms. The damage from the depth charge that sank the submarine is evident in the picture of the hull, showing the crushed in deck. I thought about what it must have been like for the crew, trapped inside as the U-Boat descended far below the water depths that it could sustain, water flooding the vessel probably well before it reached the seafloor.


Damaged deck of the U-166 as seen on the floor of the Gulf of Mexico
Damaged deck of the U-166 as seen on the floor of the Gulf of Mexico

After spending some time surveying the U-166, we retrieved the ROV and the Gary Chouest moved to the location of the Robert E Lee, a passenger freighter that had been sunk by the U-166 before it was attacked by the Navy Patrol vessel. The vessel had originally been scheduled to stop in Tampa, but was diverted to New Orleans when intercepted by the U-166. Again, we watched the screen as the shipwreck became visible, illuminated by the ROV lights.

An open hatch on the Robert E. Lee
An open hatch on the Robert E. Lee

The shipwreck of the Robert E Lee struck me as a more of familiar scene that I could relate to. The U-166 had few exterior places where people would stand or work the ship – most of the crew remained inside, even on the surface. The U-Boat was a steel cylinder with little evidence of human activity. But the images of the Robert E Lee showed open hatches, railings, and a lifeboat resting on the seafloor.

A life boat from the Robert E. Lee found on the sea floor near the wreckage

Windows and doors were evidence that the decks were filled with people, resembling a modern day cruise ship. Seeing it on the seafloor, in a debris field created when the ship hit the bottom of the Gulf, conveyed the terror that the passengers must have felt as the explosions rocked the ship and it began to sink.

It was about three o’clock in the morning when the Robert E Lee survey neared its end, and we saw the most remarkable feature of our voyage. The ships engine telegraph, a device located on the bridge and used to signal the engine room instructions on speed and direction, had been blown off and descended to the seafloor like a spear. As the ROV camera focused in, the dial shows that the telegraph had been moved to stop, the last instructions relayed from the ships officers to the engine room crew before the U-Boat torpedo blew the Robert E Lee apart.


The engine room telegraph of the Robert E Lee recording the last instructions relayed from the ships officers to the engine room crew - "Stop"

The survey ended, we retrieved the ROV and returned to Fourchon. Work on the Nakika project continued, with the pipeline carefully avoiding the site of the submarine, now a German war grave containing over 50 U-Boat crewmen. Much of the findings of our voyage have been documented and preserved in the World War II museum in New Orleans, and a subsequent voyage was made to the U-166 in 2014, supported by National Geographic.


Participating in the initial discovery of the U-166 made me realize how close to the Florida and Louisiana coasts the U-Boat campaign had occurred, and the impact it had on shipping during WWII. A few years later, the events of that day were part of the inspiration of my novel set in Everglades City during WWII, Sunniland.




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