German submarine U-166 (1941)

German Type IXC submarines were slightly larger than the original Type IXBs. U-166 had a displacement of 1,120 tonnes (1,100 long tons) when at the surface and 1,232 tonnes (1,213 long tons) while submerged.[6] The U-boat had a total length of 76.76 m (251 ft 10 in), a pressure hull length of 58.75 m (192 ft 9 in), a beam of 6.76 m (22 ft 2 in), a height of 9.60 m (31 ft 6 in), and a draught of 4.70 m (15 ft 5 in). The submarine was powered by two MAN M 9 V 40/46 supercharged four-stroke, nine-cylinder diesel engines producing a total of 4,400 metric horsepower (3,240 kW; 4,340 shp) for use while surfaced, and two Siemens-Schuckert 2 GU 345/34 double-acting electric motors producing a total of 1,000 metric horsepower (740 kW; 990 shp) for use while submerged. She had two shafts and two 1.92 metres (6 ft 4 in) propellers. The boat was capable of operating at depths down to 230 m (750 ft).[6]

The submarine had a maximum surface speed of 18.3 kn (33.9 km/h; 21.1 mph) and a maximum submerged speed of 7.3 kn (13.5 km/h; 8.4 mph).[6] When submerged, the boat could operate for 63 nmi (117 km; 72 mi) at 4 kn (7.4 km/h; 4.6 mph); when surfaced, she could travel 13,450 nmi (24,910 km; 15,480 mi) at 10 kn (19 km/h; 12 mph). U-166 was fitted with six 53.3 cm (21 in) torpedo tubes (four fitted at the bow and two at the stern), 22 torpedoes, one 10.5 cm (4.13 in) SK C/32 naval gun, 180 rounds, and a 3.7 cm (1.5 in) SK C/30, as well as a 2 cm (0.79 in) C/30 antiaircraft gun. The boat had a complement of 49.[6]

Robert E. Lee was under escort from the United States Navy patrol craft PC-566[9] about 45 mi (72 km) south of the Mississippi River Delta when she was torpedoed by U-166 on 30 July 1942. PC-566 immediately attacked, making her approach vector outside the view of U-166's periscope, and claimed to have sunk the U-boat with depth charges. Upon returning to port with the survivors of Robert E. Lee, the Navy did not believe the account provided by PC-566's skipper LCDR Herbert G. Claudius, USNR. Claudius' tactics were criticized, resulting in his reprimand and removal from seagoing command.

On 30 July 1942, a United States Coast Guard J4F-1 Widgeon amphibious aircraft spotted a U-boat around 100 mi (160 km) off the coast of Houma, Louisiana. The aircraft attacked and it appeared that the U-boat was hit in the attack. U-166 was reported missing in action on 30 July 1942, which coincided with the American aircraft's attack on "a U-Boat", leading to the aircraft being credited with the sinking of U-166, with the loss of all 52 crew members. Both aircraft crewmen were decorated for the action.[10][11]

A gun on the deck of the sunken U-166

In 2001, when the wreck of Robert E. Lee was located in more than 5,000 ft (1,500 m) of water, the wreck of U-166 was also located, less than 2 miles from where it had attacked her. An archaeological survey of the seafloor prior to construction of a natural gas pipeline led to the discoveries by C & C Marine archaeologists Robert A. Church and Daniel J. Warren. The sonar contacts consisted of two large sections lying roughly 500 ft apart at either end of a debris field that indicated the presence of a U-boat.[12] Petroleum companies operating in the Gulf of Mexico's outer continental shelf are required to provide sonar data in areas that have archaeological potential. BP and Shell sponsored additional fieldwork to record detailed images, including a gun on the deck aft of the submarine's conning tower.[13]

Charles "C.J." Christ, from Houma, spent most of his life searching for U-166 and was involved in the final identification of the U-boat.[14]

The site where U-166 lies, at 28°41′N 88°42′W, has been designated a war grave because its crew of 52 is entombed there. It is protected against any future attempts to salvage it.

Oceanographer and National Geographic Explorer-in-Residence Robert Ballard explored and mapped the wreck in the summer of 2014 with remotely operated vehicles, where they noticed that the submarine's bow had been blown off and found rested on the seafloor 100 feet away from the main hull. They determined that the bow of the submarine was destroyed, apparently by a depth charge that landed on the forward deck, exploded, and caused an internal detonation of the submarine's own torpedoes, which broke off the bow. If so, this would be one of the few successful submarine kills caused by direct contact from a depth charge, as typical attacks relied upon depth charges exploding a short distance away to inflict repeated hydraulic shocks that would eventually crack a submarine's pressure hull.[15][16]

Initial credit for the sinking of U-166 had been given to a Grumman G-44 Widgeon, but the position of the wreck made it clear that this should have gone to the submarine chaser PC-566.[10][17][18] On 16 December 2014, the Secretary of the Navy Ray Mabus posthumously awarded the captain of PC-566, then-LCDR Herbert G. Claudius, USNR (later CAPT USN[19]), the Legion of Merit with a Combat "V" device for heroism in battle and credited him with the sinking of the U-boat. "Seventy years later, we now know that [Claudius's] report after the action was absolutely correct," he said. "[Claudius's ship] did sink that U-boat, and it's never too late to set the record straight."[20][21]

Results of a study released in February 2019 showed that the wreck of U-166 was being badly damaged because of the 2010 Deepwater Horizon oil spill. Seabed bacteria, feeding on the oil, were causing the damage.[22][23]

• One of the foremost authorities on the subject is Charles "C.J." Christ, from Houma,[25] who spent most of his life searching for U-166. His personal account about his search and the final locating and identification of the U-boat can be found in a local newspaper, The Houma Courier: C.J. Christ "WAR IN THE GULF: German submarine, U-166, found in the Gulf of Mexico" (The article can be found online as reprint by another local newspaper, The Daily Comet).[26]

• Helgason, Guðmundur. "The Type IX boat U-166". German U-boats of WWII - uboat.net. Retrieved 7 December 2014.
• Hofmann, Markus. "U 166". Deutsche U-Boote 1935–1945 - u-boot-archiv.de (in German). Retrieved 7 December 2014.
• The Story of U-166: The Gulf of Mexico's Lost U-Boat
• Photograph and sonar image of the Robert E. Lee
• The U-166 - NOAA
• WWII German UBoats
• WWII Gulf of Mexico Shipwreck Survey Expedition 2004 - NOAA