The problem with the marine environment is that its to flat and boring. If the developers are going to add naval combat, they should add more interesting marine features, like:
- foggy/misty areas with reduced visibility for some cover
- lagoons, rivers, lakes for interior continent access, surrounded by high cliffs/forest cover
- island chains with erupting volcano's poking above the surface
- large wet and dry caves (no accessing via warp gates) with surface access along its length
And the
players should definitely be able to swim (none of the walking on the ocean floor). Perhaps instead of getting fatigued and drowning, have a giant marine creature come and eat you after a certain amount of time (client side).