Great ideas, guys. Thanks!
In this case the movement of the ship looks quite OK to me, so I'll try to focus on other things.
Here is the latest version. I reduced the blue water area (it looked a bit unnatural to me), which reduced rendertimes as well
For the frontal part of the wake I added a masked white fake stones shader. Using a cloud layer didn't really look good. I couldn't get a terrain conforming cloud, so I thought about trying other possibilities. Maybe the fake stones should be a bit more prominent... I'll keep on testing!