Deepolis

Deepolis is a free-to-play MMORPG from Bigpoint that takes place in the depths of the ocean where you command a submarine and wreak havoc upon your enemies.

There are three playable factions, each with its unique story and characteristics. The quest-driven story will have you explore the deep-sea and perform faction related tasks that will many times have you attack enemy factions’ facilities and convoys. But you can always skip the PVE part and jump into PVP action hunting down real-life players for reputation and loot. The game features an impressively depicted sea world with detailed 3D graphics and a very easy to master combat system with stunning visual effects. If this is your kind of game genre and you would like a good story presented in a completely original setting, then Deepolis will satisfy you immensely.