This is a video of a US Navy ship going from full speed to a dead stop. Partway through, you can see the water in the ship’s wake start to change color. It starts becoming noticable about the 40-second mark, and then it builds from there.
Does anybody know what causes the change?
I didn’t notice any color change other than that due to bubbles making it lighter. Is that what you mean?
Just aeration of the water due to turbulence from going full astern. Entrainment of bubbles.
At the very beginning, if you look at the far end of the wake in the distance, it’s a distinctly lighter color than the surrounding sea. Up closer the wake is almost entirely white. But once the white settles down, the wake is a lighter blue than the sea.
The reversing just brings the same color up close and personal by mostly removing the white foaming water, which is now much more alongside the ship than immediately astern.
The sun appears to come out from behind clouds around 0:30 (look for shadows), but it also looks like the water is more oxygenated toward the end of the video.
The sub tender I served on in the Navy did the same thing but not this dramatic. The tender was only moving at 12 knots and had a single screw. This ship was moving a lot faster and likely has twin screws. The ship I was on did this as a show as we cruised into the harbor at Acapulco back in 1979.