I would imagine the floodlights from the boats would be at a low angle, trying to light up as much surface area as they can. Lighting the surface of the water would show up in the pictures better than the equivalent city wattage that would only show incidental light escaping from where it's used.
This gave me a flashback of the search lights on trucks that use to mark supermarket openings and new car years at the dealers. They were gas powered and looking into the unit at a low angle it didn't look like those rows of little flames could produce that powerful beam that flashed the Batsign on the clouds.
