In the part where you cross the marshes on a motorboat, there is fog everywhere, in which it is necessary to wear a breathing mask and at the same time the view is very limited. From the ground or the water you cannot see the surrounding houses at all. This is a normal condition.

By the time one reaches the dock on the other side of the marsh, the fog should have cleared, so there is no need for a mask and the view of the surrounding houses is restored.

Unfortunately, sometimes a mistake is made and the fog does not disappear. From this point on, the fog remains until the end of the game and it's almost unplayable. The only way to see through the fog is by using night vision.

I recommend backing up your saved positions before entering the swamp. If the bug shows up, at least it would be possible to undo the backed up positions and try again. Another option is to try to walk the entire swamp without using the save and then retrieving the position.