I suspected when I posted above it was a related phenomenon and not Fata Morgana itself. This is an optical illusion. Fata Morgana is a legit optical effect that subsequently can produce an optical illusion if our brains perceive the distorted image as something else.
The picture didn’t look anything like the examples in the Wikipedia article. They’re always easy out at the edge of the horizon. This boat was far too close.
But the Wikipedia rabbit hole about horizon optical effects led me to reminisce about the time I saw the green flash. That’s a fun memory.