Submerged Submarine Sinkings

Britain's Navy News tells of a BBC documentary tonight on the sinking of U-864 by HMS Venturer in Feb. 1945, which they say is the first ever sinking of a submerged submarine by another submerged sub:
U864 was torpedoed by HMS Venturer near Bergen, Norway, in February 1945 while both vessels were submerged. She sank with all 73 hands – and with a cargo of Messerschmitt jet engine parts, missile guidance systems, and mercury, all bound for Japan.
Intercepted radio messages had alerted the Admiralty to U864’s secret mission (codenamed Operation Caesar), and Venturer lay off Bergen waiting to intercept the U-boat as she left Norway bound for the Far East.
Venturer picked up the German boat on her ASDIC (the original British name for sonar), and visually sighted U864’s periscope sporadically, tracking the submarine for a good hour before firing a spread of four torpedoes from a range of about 3,000 yards; one found its mark, destroying the German vessel.
The wreck was found three years ago and Norwegian salvage experts are preparing to recover it because of the danger the mercury poses to the environment.
I had thought I remembered reading about an American sub that sank a submerged Japanese sub in WWII, but couldn't find it during a quick Google search. Does anyone know if there are any instances of a U.S. boat sinking a submerged enemy submarine?