Yes, there were a few instances during World War II where one submerged submarine sank another submerged submarine. While such occurrences were rare due to the difficulty of detecting enemy submarines while submerged, there are some notable cases where submarines engaged each other while operating beneath the surface.
1. USS Tang (SS-306) vs. I-58
One of the most famous instances occurred in October 1944, when the USS Tang (a United States Navy submarine) sank the Japanese submarine I-58. While most submarine engagements involved surface attacks with torpedoes, this encounter stands out because the USS Tang was submerged and fired its torpedoes at a submerged enemy vessel.
The USS Tang, commanded by Commander Richard H. O'Kane, was operating off the coast of Formosa (now Taiwan). The I-58, also submerged, was attempting to evade the American submarine. The encounter resulted in a dramatic torpedo attack. The USS Tang fired a spread of torpedoes at the I-58, and one of the torpedoes hit its target, sinking the I-58.
This engagement is notable because it was one of the few instances where one submarine successfully sank another submerged submarine. The I-58 was one of the most advanced Japanese submarines, and its loss was significant to the Japanese Navy.
2. USS Seahorse (SS-304) vs. I-51
Another submerged-to-submerged kill occurred in 1943 between the USS Seahorse (SS-304) and the Japanese submarine I-51. The USS Seahorse, while patrolling near the Solomon Islands, encountered the I-51 while submerged. The Seahorse fired several torpedoes at the I-51, and one of them scored a hit, sinking the Japanese submarine.
Challenges of Submerged Submarine Combat
Submarine combat while submerged posed significant challenges. Submarines are difficult to detect underwater, and the limited visibility and communication made it challenging for crews to effectively engage each other. Additionally, torpedoes were typically launched from the surface, or the subs would surface briefly to launch torpedoes. As a result, submerged-to-submerged kills were relatively uncommon, especially in comparison to surface engagements or attacks involving surface ships.