It looks like a combination of particles and a subdivided plane with an animated height map or simply random z movement of verticies.
You can get a plane, apply a dotty texture (maybe making it animated too would help) then either write script to move the verts or use shape keys or an armature to animate the plane.
There’s a few resources in the resource forum which recreate water movement through vertex manipulation. I’d recommend trying to find them first.
On the other hand, you’re not likely to have a long loading time in a blender game. We don’t have to load from a DVD so we don’t have that bottleneck. You can use dynamic loading (LibLoad) but still you’re not likely to have a loading time of more than a few seconds.
My most complex game, with over 12000 objects took about 10 seconds to load.
Also during the loading of scenes blender locks up, you can’t have a progress bar or other things unless you write a script for loading the scene’s objects bit by bit. In that case you start with an empty scene and start placing objects in there automatically using a placement script set to load a small amount of objects each logic tic. If you start with stuff nearest the camera then people probably won’t even notice that the level is still being loaded.