The World War II Uboat simulator UBOAT from developer Deep Water Studio and publisher PlayWay has debuted on Steam in early access. The game was a number one best seller at launch. It’s steam page is at: https://store.steampowered.com/app/494840/UBOAT
Check out the game’s launch trailer to see how intense the underwater battles can be:
The full game is expected to release sometime in 2020.