There is something amiss in your system. For SH4 to play properly, you want to match your video display to Windows first, ie: 1280x1024 LCD display ("Native") of mine is using the Windows "1280x1024 (recommended)" resolution setting in the "Screen Resolution" of Control Panel. The SH4 game is also set to that same resolution. When installing SH4, do not install it in a "Program Files" folder, Windows will trash mod activations there. Use your own folder. When installing SH4, also install the DirectX v9.0c that comes with the game. You don't need any of the other stuff with it. After installing the game, I make certain the files aren't write-protected, and then I used 7zip to make myself an archive file of the inside of the "Silent Hunter 4 Wolves of the Pacific" folder. That's my backup for when things go wrong with mods (which they do). I can also make a new folder, name it what I want, and unzip the archive in there to create another version of the game. I make certain the game files are write-protected, and I use MultiSH4 to make a new Save folder for that new copy. That way, I won't cross-contaminate the copies of the game I already have. I will then run JSGME and use "Tasks - Generate a snap shot of game files" before applying a mod to the new game copy. If I happen to "update" a modded SH4 copy with a new version of the mod, I will deactivate the old mod, empty the Save folder for that copy, then activate the new mod. Gamplay settings, screen resolution and the like don't keep, but that's the price of modding. One last thing to look for is the Large Address Aware. You may have run it on the file and looked like it "took", but it might not have. Again, make sure it is not write-protected. Run LAA again, and use the "Intermediate" mode, and check the two columns for "True" and "False".
Something is interfering with your game being able to properly display. Something is trashing a portion of the view near your submarine. It might be in the save folder. it might be in the game folder, and it might be in the use of a big mod, but LAA did not "take" correctly. Just remember that it is an old, fickle game. But it sure is fun...
