This was taken during the blue hour, when the light is soft and dramatic. I used a long shutter speed with a 3 stop ND to slow the water even more to give it a misty ethereal effect. The lighthouse is Beavertail, located on the coast of RI.
Camera: Canon 5D Mark III, lens: Canon 17-40mmL f4, Gitzo tripod.
camera settings: f18 at ISO 800 for 20 seconds