Actually only one U boat on the bottom near key west was U2513 a type XXI post war sank by USN during asroc practice. Diveable wreck site, for tech divers.. No other were sank in the gulf except one, U166 type IXC during Polkinschlag operation. However several boats were sank or damaged by U boats off of the lower keys. Most prominent was U571 VIIC Kaloin Helmut Mohelman sank 6 ships in 5 days off Key west early July 1942. The sinking of the Brit cargo ship Umtata was a significant sinking with several historic circumstances. Umtata was sank by a U boat previously in the shallow harbor of Curaco and was subsiquently raised with its cargo of copper ore, and being towed to Ft Lauderdale from Key West for engine repair. U 571,(Not the ficticous movie one) intercepted the ship and ocean going Moran tug in the Hawk Channel off of the Aligator reef light. Mohelman was on the surface just before sun up charging batteries in a rain squal and saw the easy target approching and opened fire with the deck gun. The skeleton crew on the ship chopped the tow with an ax and the tug proceded on for a short time. The crew was alowed to abandon in the life boats. Mohelman continues the attack with the 88mm until a patrol craft spotted the sub.Crash dive was out of the question in the shallow channel so U571 submerged to perriscope depth. During that process the tug had turned and tried to ram the sub unsuccessfully. (only incident during the war of an unarmed tug attacking a U boat.) The PC cutter was slow arriving and picked up the survivors but not before U 571 torpedoed the Freighter. One other ship that was any significant size and target that Mohelman attacked was the SS Pensylvania Sun T-2 tanker torpedoed and set on fire just a few miles west of Key West in that same week. Mohelman was awarded the Knigts Cross for that mission, He survived the war. However the U 571 was sunk in the eastern Atlantic later in the War.