One of our best photography experts has weighed in on the side of this being a light on a boat. Here is his comment:
"Just measure the distance between the leading edge of the top light in the first and second pix. Let that distance equal 4.5 seconds. Then measure the length of the top light's streak. That will tell you the shutter speed. Assuming Crowe is right about the frame rate, the shutter speed seems just about right for a night exposure with a Canon 5D. And given that lens's field of view, 8kph (max legal boat speed in that situation) works out just about right with a margin of error of, say, +/- 50%, max."
"If the object had been moving at 80kph either he'd have missed it completely or a single streak would have covered the full width of one frame, and one frame only."
"None of this has anything to do with camera-subject distance. It's mainly a matter of field of view (i.e., how wide or narrow the lens was zoomed) relative to the lateral speed of the boat."
In your Out There editor's opinion, this case is closed--darn it!