If using the <F12> key to get to the external camera, or the menu buttons, you should be near the surface, about 15-20m above the surface. You should not be able to use the bridge or deck gun cameras when below... Did you clear the Save folder after activating the FotRSU mod(s)? If not, you need to do that, and then start a new career (C:\Users \UserName \Documents \SH4).
Open the JSGME.exe file in your game folder, click on the "Tasks..." link in the middle of the app window, and choose "Export activated mods list to..." and choose "Clipboard". In your next posting here, use the <Ctrl><V> key combination to "paste" that list into the text box here. That way, we can see what you have activated for your mods, and also the folder the game is in.
