Something I didn’t really get across in my video was an accessible explanation for the difference in the color of the water surface being so abrupt. Here’s a somewhat less abrupt example:
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And the full context:
Here you can see the line between dark and light (the “false horizon”) does not extend all the way across the actual horizon. On the right, you can see the water is distinct from the sky all the way up to the ship and the “real” horizon. Especially if you boost the color contrast a bit.
The simplest explanation is just a change in the texture of the water – i.e. it has smaller waves ... Read even more