The attack on the Hoover Dam in Dec 1944 that failed has referance to a U boat that fits the discription of a XXIII. The boat was captured after running aground in the Colorado river before it could reach the dam. The wreck was recovered with the Rheintochter R-1 Missile that was going to be used. The remains of the wreck were to thr muroc dry lake area and used as a target for military aircraft the remainder of the war,and post war. Eventually the area was flodded and most of the wreck is gone. However some artifacts were taken by the Navy crew that were assigned to recover the wreck from the sandbar in the river. Looking at the stats of the disposition of all the boats, I came across a discrepancy in the run of production numbers vs U number.U4707 4708 and 4709 work,#949, #950 and #951. The U4708 with coinciding work #949 there is no explainable disposition Operation deadlight or capture or destroyed in the yard. The Submarine was decribed as small, around 100ft higher foredeck no guns visible, after deck lower to the water with a missile on the rear deck. The boat was said to have been transported by raider ship to Japanese base in SE Asia where the 5 parts were assembled and towed by a submarine to the secret Japanese base in La Palmas Baha Mexico. From here the missile was assembled on the deck and sub was talen to the Colorado river delta, where it made its way, surfaced up river to the Laguna Dam, 13 miles ne of Yuma, It was taken apart again and transported by trucks up river several miles then re assembled, by German laboreres simpithetic to the Nazis. This point a small group of escaped German u boat prisoners with their Captain Wattenberg. were to rondezvous with the skeleton crew and proced up to the Hoover Dam and launch the missile. The majority of the escapees and Wattenberg were re captured and the mission eventually failed when the small skeleton crew plus a coupel escapees that made it ran aground on a sandbar in the river and were discovered by locals. Its my humble opinion the remains of the wreck are still on the muroc lake bottom somewhere.