The US Navy ComSubPac encouraged aggressive behaviors of their submarine captains. This also placed their boats well into harm's way. The USS Piranha was sent to patrol the Yellow Sea; between mainland China and what is now Korea. The Yellow Sea's average depth is only around 144 feet. Not an easy place to hide a submarine that's longer than a football field. The USS Piranha was on patrol January 1945 and intercepted a IJN medium convoy about 200 miles ENE of Shanghai just after sunrise in heavy fog. Good conditions for the boat. The attack was pressed and 2 large merchants were sunk, and a heavy tanker crippled when a patrol craft's sonar detected the Piranha. One stern torpedo stopped that attack, and the Piranha headed North to escape and finish the tanker, when another patrol craft found the now surfaced boat and shelled her. Damage was not enough for the captain to finish his last attack on the damage tanker, and fired his one forward tube at 1400 yards out, then crash dived to periscope depth. In the fog of battle, the captain, whose boat had been loaded with 2 different torpedo types- the older MK 14 that tended to run too deep, and the newer, wakeless and improved Type 18-2, set the depth for his last rear tube to 4 feet and fired on the approaching patrol craft. The torpedo was a MK 14, not the the 18-2, and went below the attacking ship. The steering gear was damaged, so evasive maneuvers were limited. Captain set the boat's depth to 82 feet, engines full astern, hoping to pass under the attacker, fire one last forward tube, and then escape. He had done this before successfully, and it was their only chance at survival. As the Patrol craft passed overhead, they had set their depth charges shallow, and, unfortunately, the Piranha was lost with all souls like the other 22% of US submarines lost during WWII.
