For play in HC game version 2022.027 (matrix patch) or newer. Westpac BS and using database HCWW 101110.
21 January, 1941, a Japanese invasion fleet of one light cruiser, ten destroyers, four minesweepers, three submarine chasers, three patrol boats and sixteen transport ships left Tarakan for Balikpapan, (oil rich areas of Borneo). A MLD Dornier spotted the fleet that same day, but heavy clouds with strong winds and prolonged rain prevented the plane from shadowing the fleet. On the next day, U.S. Navy submarines S-40, Pickerel, Porpoise, Saury, Spearfish and Sturgeon were ordered to intercept the fleet. Later, they were joined by Dutch submarines K-XIV and K-XVIII. Sturgeon fired several torpedoes on the convoy and reported sinking three ships. However, postwar records failed to confirm any damages to the convoy.
In this scenario a simplified version of the situation is recreated with the submarine force intercepting the south bound invasion fleet at the narrow northern entrance to the Makassar Strait.
(ScreenShot US SS Porpoise, http://www.navsource.org/archives/08/08172.htm, Public Domain, https://commons.wikimedia.org/w/index.php?curid=2030041)