It turns out that when you look the other direction in the U-boat, that the slope is correct.
As it turns out, when you dive, the viewpoint of the "camera" will tilt in one direction. So, when you look to the port side and you look to the starboard side, the slope angle of the boat will seem to reverse itself, one being correct and the other being wrong.
Also, sometimes no tilt at all is noticable, in my experience.
__________________
.-. --- ..- --. .... ... . .- ... .- .... . .- -..
|