From the Depths.
It's in early access though but it's a lot like you described.
Basically it's a thing where you can make a boat, sub, flying machine, or water base with guns and things. It's really in depth (ha) and it will take a bit to get used to.
Or if you're like me, spawn ai with pre-made things (there's a metric ton) and watch them fight to the death because that's a thing.