Hitman of course it's not the same to compare a mountain and a ship at a horizon distance..
I found something that might proove the visibility range in this mod not accurate at all compared to RL:
http://en.wikipedia.org/wiki/File:Ho...he_horizon.png
Correct me if I'm wrong but as far as I know while standing on a beach the horizon is probably at 11 km away. The big ship is a tall object so it can be seen from 14-16 km max with a naked eye.
Well binoculars might do the trick to see further and this would add +4km to visibility ? Hmm..
And binoculars should be from WW2 time, not the present..