In the summer of 1942, war came ashore without ever touching the beach. German U-boats prowled the Gulf of Mexico, hunting the tankers and freighters that kept America moving. Their torpedoes flashed beneath waters familiar to shrimpers, pilots, and merchant crews from Florida to Texas.
On July 30, that hidden campaign reached the passenger freighter SS Robert E. Lee. One torpedo sent the ship down southeast of the Mississippi River. Then the small U.S. Navy patrol craft escorting her turned toward a periscope and fought back. Nearly six decades passed before the seafloor revealed what happened next.
War Reaches the Gulf Coast
The Gulf may have looked sheltered on a chart, but it was a vital wartime highway. Oil, fuel, troops, and cargo moved through its ports while German submarines slipped through the Florida Straits and Yucatán Channel. According to the Bureau of Ocean Energy Management, more than 20 U-boats operated in the Gulf during 1942 and 1943 and sank 56 vessels.
That toll turned familiar coastal waters into a battlefield. Crews sailed under blackout rules. Lookouts searched the horizon for wakes and periscopes. A routine passage could become a fight for survival in seconds.
The Type IXC submarine U-166 entered that campaign in the summer of 1942. By late July, it was positioned roughly 45 nautical miles southeast of Southwest Pass, where the Mississippi meets the Gulf.
Robert E. Lee’s Final Passage
Robert E. Lee was a passenger freighter carrying 407 people: 131 crew members, six merchant marine officers, and 270 passengers. She was under escort by the 173-foot patrol craft PC-566, a compact warship built for the hard, unglamorous work of coastal defense.
On July 30, U-166 fired. The torpedo struck Robert E. Lee on the starboard side, and the ship began to go down. Ten crew members and 15 passengers died. Most of those aboard escaped into lifeboats and rafts, but the loss was sudden and violent—a reminder that the Gulf campaign was fought within reach of America’s own ports.
For the escort crew, there was no time to dwell on the sinking ship. PC-566 spotted a periscope and moved to attack.
PC-566 Turns Toward the Periscope
A submarine’s safest moment came after firing, when confusion often covered its escape. The men aboard PC-566 denied U-166 that advantage. The patrol craft rushed the suspected position and dropped depth charges into the Gulf.
The explosions churned the water, but no intact submarine rose to the surface. There was no easy proof of a kill. U-166 simply disappeared, lost with all hands. In the immediate aftermath, the Navy did not credit PC-566 with sinking it.
That uncertainty would shape the official story for decades.
The Wrong Submarine Gets the Credit
Two days later, on August 1, a U.S. Coast Guard J4F Widgeon amphibian aircraft attacked a surfaced submarine off Louisiana. Chief Aviation Pilot Henry White flew the aircraft with Radioman First Class Henderson Boggs aboard. After the war, the Navy credited their attack with sinking U-166.
The record seemed settled, but the positions never fit comfortably. The aircraft attack took place more than 100 miles from the place where Robert E. Lee had gone down.
Later research showed that the Coast Guard crew had attacked U-171, which escaped. White and Boggs had made a real and courageous attack, but it was not the end of U-166. The answer remained on the bottom of the Gulf.
A Pipeline Survey Solves the Mystery
In May 2001, a routine pipeline survey changed the history books. C&C Technologies, working for BP and Shell, detected wreckage in nearly 5,000 feet of water. Remotely operated vehicle footage and archaeological analysis confirmed that the wreck was U-166.
Its location told the story: the submarine rested within about a mile of Robert E. Lee, not at the distant site of the Coast Guard aircraft attack. Damage evidence and the wreck’s position supported the conclusion that PC-566 had sunk it with depth charges immediately after the torpedoing.
A commercial survey had solved a 59-year maritime mystery. The proposed pipeline was rerouted to protect the site, leaving both wrecks as grave sites and archaeological witnesses to the battle.
Two Wrecks, One Battlefield
Robert E. Lee and U-166 now rest close together in the deep Gulf: attacker and victim, the remains of one brief engagement preserved on the same seabed. Of all the German submarines that entered the Gulf, U-166 is the only one known to have been sunk there.
Their discovery also corrected the honor due to PC-566. Small patrol craft rarely carry the fame of battleships or carriers. Their crews escorted vulnerable ships, watched dark horizons, and acted with whatever evidence they had in the moment. On July 30, 1942, one of those small crews turned toward danger and made its attack count.
That same quiet readiness runs through many Coast Guard and small-craft stories, from the tethered rescue swimmers of Escanaba to the four-man Pendleton rescue. The vessels were modest. The seamanship was not.
What Gulf Sailors Should Remember
The lesson of U-166 is larger than a corrected line in a wartime ledger. The sea keeps evidence long after eyewitnesses are gone, and patient research can restore a crew’s place in history. Technology found the wreck, but disciplined archaeology turned wreckage into an answer.
For sailors along today’s Gulf Coast, the story changes the water beneath the bow. These are not merely vacation seas. They hold convoy routes, war graves, and the remains of people who met the enemy close to home.
Fair winds honor every kind of mariner—the celebrated cutter crew and the nearly forgotten patrol boat alike. Explore more Coast Guard traditions and history, or visit our Coast Guard Life collection for designs shaped by that enduring service.