Humans make assumptions, it's in our nature. They are frequently wrong.
Here, it is assumed that the UAP is a material thing, that is, made out of matter, like metal. But it may be a kind of ball-lightning, made of plasma, or an optical phenomenon like the aurora, where the light emission arises from ionized air molecules or atoms. Or atmospheric effects, vortices spun off from a tornado, weird cloud effects. Few know about the Green Flash. Reflections are everywhere. Muons and other cosmic rays are all over the place.
Plunging into the sea (?) and never coming back up again is what the sun does every sunset over the Pacific.
Speed is often an illusion. Everyone knows that "nothing" can move faster than the speed of light, c. However, the point of intersection between the blades of a very long scissors will move faster than c as the scissors close!
Why the sky is blue and why there are rainbows were once UAPs.
I recall visiting the Johnson Space Flight Center and a very nice docent was taking a group of tourists around. A woman asked, "well, did we find any new metals on the moon?" I cringed. We know all the metals and elements there are--92 natural ones. They are all listed in the Periodic Table. You can't have element 55½.
(actually, there are only 91; know which one is excluded?)
I am quite sure that these UFOs did not come a galaxy far, far away commanded by blue-green algae with a yen for voyeurism. For one thing, I am reliably informed that the budget for such adventures in Alpha Centauri has been slashed following the explosion of their 4th moon. Their research has been refocused on why forks and keys do not stick on their foreheads, if any.
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