[Hitman]

It's unfortunately supposed to look like that. In SH3 you won't get a clear horizon line that cuts the ships as in real life, but instead the earth curvature is simulated invertedly, i.e. it curves slowly UPWARDS from your position to the horizon, and that way it progressively hides ships that are at the same height as you, instead of the game making the ships slowly "sink" under the horizon. The problem is that this way you would see the earth still curving upwards beyond the ships, hence the developers added a sea fog that blends sky and sea and hides that effect. The side-effect is the one you have noticed....ships seem to float in the horizon fog.