A CPL would also likely kill the reflection which for me was a key element. I used the reflection of the lighthouse and reflected sky as part of the image...didn't really see it as glare. Yes it was quite calm. The clouds didnt move much at all either.
Are you sure? I have a shot here with a CPL (and GND) and the reflections of the clouds are very visible, but the glare is gone and you can see the surface..