I think it's the water too. What time did you take this shot? It seems that they might be some boat that pass by the scene that may affect the reflection ( I see a streaking effect across from left to right). How long was your exposure btw? There wasn't any exif that can be seen, or maybe I'm not so familiar.
Btw, if you shoot RAW, you can adjust your noise filter level so you don't have to shoot several shots with different noise filter levels, and save some time to do other tests. Do note that "noise filter" in Oly viewer it's called noise reduction (assuming you use Olympus viewer)...But on the camera setting, noise reduction refers to "dark frame subtraction" to help reduce hot pixels in long exposure shot, this for me is always set to Auto, so that the camera will take 2 shots and take twice the processing time. Hot pixels can be an issue with Pen after several LE shots. Just to mention as I find the terminologies kinda confusing
Btw, if you shoot RAW, you can adjust your noise filter level so you don't have to shoot several shots with different noise filter levels, and save some time to do other tests. Do note that "noise filter" in Oly viewer it's called noise reduction (assuming you use Olympus viewer)...But on the camera setting, noise reduction refers to "dark frame subtraction" to help reduce hot pixels in long exposure shot, this for me is always set to Auto, so that the camera will take 2 shots and take twice the processing time. Hot pixels can be an issue with Pen after several LE shots. Just to mention as I find the terminologies kinda confusing
