I don't find myself on many ferries when the night sky is completely dark. Late night ferries are always pretty empty, with just a handful of passengers aboard. It's a strange sensation being out on the water and seeing nothing around you except the glow of city lights off in the distance.
Typically, I'm running around the ferries with my camera searching for shadows created by the direct sunlight, but I do love the way the beams of light on the passenger deck cast a warm glow on the old leather booths at night.