Here's something I came across while working on a fast sailboat design. In this particular design, the side force on the boat, when going fast (40 knots and above) would actually exceed the total weight of the boat and crew. Therefore, the airfoil-shaped centerboard (a type of keel that can be retracted) would have to generate an amount of lift (directed sideways) roughly equal to the weight of the boat. Structure was one concern, hydrodynamics another.
So, suppose I did a test of two competing foils, with one facing one way and the other facing the opposite, mounted from a fast motor boat. With their lifts canceling (more or less) the boat could go in a straight line (more or less) instead of being pushed sideways as would happen if I tested one foil at a time. I didn't actually do this at night, but I might have, just for fun and additional thrills. Suppose while testing, I saw blue light emanating from the water. Aside from the obvious – hallucinations – what other causes might there have been for by seeing blue light? Could I look for something on the foils to prove (or strongly suggest) that the light occurred for the reason you propose?