Going from memory here, but on the first patrol out of Fremantle following short assignments to Manila and Surabaya (probably in mid-to-late March 1942), I got a warship sound contact after passing the entrance to Lombok Strait. It soon evolved into many multiple mixed contacts, all in the approximate center of the Strait, but moving generally to the Northeast. Still surfaced, I went Westerly and hugged that side of the Strait out of visual range until gaining a position ahead of the mass of sonar contacts. I was nearing the end of the Strait with the contacts clearly to my Southeast when I turned due East to a point about 1/3 the way across. It now seemed that the contacts were moving towards me, or at least Northerly, so I submerged to a point about 80 feet below the reported thermal layer and waited.
Sure enough, they came into range, being led by a Kuma Light Cruiser. It was surrounded by 6-8 DDs and DDEs, but there was a clear gap in the NNW sector as they came towards me. I came to PD and found the Kuma about 2000 yards to my East. I sent 2 MK14's to him, with both hitting and setting him afire. I dove deep again and headed Southeasterly where the bulk of the sonar contacts lay. Upon rising to PD again, there were numerous small transports all around, moving in various directions but generally NNW. I sank several with the bow tubes, then hightailed it East. The escorts made no meaningful attempts to find me! Coming back up to PD, there were 2 more transports and another light cruiser about 1500 yards to my stern. All three went down with our stern torpedos. Again, there was no real pursuit, possibly because we went deep and fast almost immediately on firing the torpedos, dropping a decoy (dubious value) and heading NE. The convoy eventually regrouped and headed NW towards Surabaya via one of those two channels East of Surabaya. We reloaded all tubes, surfaced, and proceeded up towards the Makassar choke point, our intended destination.
The tonnage claimed that day was not great, but the number of ships sunk was impressive: 2 light cruisers and at least 4 or 5 small transports, at a cost of 12 torpedos. And it was fun!