The game doesn't really force you out of the bottom space unless the red creatures spawn below you. Maybe you could add some fish that travel vertically. That could help out the dynamic.
The lighting is also really cool, especially when you start playing and the water gets illuminated. It looks nice!
Personally I had performance problems. The game ran around 15 fps. Of course Unreal is quite demanding but there should be a way to tweak it. Overall as a first project in Unreal it's not bad. Good job!