Sub Command is from the same team (Sonalysts) of developers,
plus, you get to drive around the Akula and Seawolf classes. If you
liked Jane's 688, then I highly recommend Sub Command. If i
remember correctly, they even model a few Malaysian ships in-game
and you can create your own littoral missions in SG + Straits of
Malacca waters (Maps are lo-fi though).
Doing your own TMA and working at a successful shot is definitely
one of the most satisfying experiences in the game.