This is most likely a polarization effect caused by the airplane window itself. Aircraft windows are made from multiple plastic layers, and those layers can behave as birefringent material. When polarized light from the sky or reflections passes through them, different wavelengths are altered differently, producing colorful patterns from constructive and destructive interference.

In short: the “psychedelic” colors were not really in the water—they were created by polarized light interacting with the layered plastic window. That also explains why shots not taken through the window looked normal.

The fact that you could see the effect in the EVF but not clearly with your eyes is consistent with how camera viewing systems and exposure can make subtle polarization artifacts more noticeable.