The Cruel Sea
From Scenario League Wiki
This scenario covers the ‘Battle of the Atlantic’ between late 1940 and 1944. The scenario is intended to be played as the Germans, though other civilisations may also prove entertaining (if a bit easy).
In this scenario you play the commander of one of the major navies. As a result, you only command naval, and some air forces, and must follow any orders given by your commander in chief, no matter how stupid they seem.
Scoring is achieved by comparing loss to kill ratios and entering them into one of the attached spreadsheets.
This scenario is designed to be hard. This is intended to simulate the fact that Germany never really had a chance of winning the Battle of the Atlantic (as Admiral Donitz conceded after the war).