PhysX doesn't support ocean-physics. It supports particle fluids, but they are not designed for such big volumes of water. Thus, you can't use a native PhysX feature for that particular task. Though, NVidia is working on such a feature, which would be again for PhysX 3.x, which is not support by the current Gamestudio plugin - you would have to write a completely new one.
I was asked for this lately, too. My answer was since the premise was that Gamestudio is the engine for the project, to write a fishtank simulation (
like this), based on heightfields and transfer the dynamics to a terrain. In Skyrim, Bethesda implemented a very basic version of that for pools of water to render a normalmap or something to simulate dynamic rings of water, which appear when the player walks through the pool. In that case they do just normalmapping, but for ocean physics you need a real deformed mesh in my oppinion, so, it is worth it.
Together with a scene description in 2D (like Superku proposed) and a description where ships are and what (oriented) shape they have, this could lead to a very nice water simulation (if multithreaded, it could be also not so CPU heavy as one might think, given that the user has multicore CPU which is nowadays standard).
Together with a cool water shader, you could achieve a very nice water simulation.
But this drives only the water simulation. The ship simulation can be done with force fields, which is in fact a PhysX feature, though, not enabled in the PhysX plugin. As far as I know, Slin works with PhysX forcefields for the very exact same problem and if you ask him, he might commit that to the repository of the open source PhysX plugin on SourceForge.
