I should also note that Kappas and all similar water sprites have the diagnostic feature of having very thin arms and legs like a monkey would have and not necessarily what an ape or human would have.
Tyler has adjusted my opinion on the Kappas and Gambo since he has started posting, and since he has started posting I have also started revising my opinion about the supposed Pterosaurian sightings: I now think that many reports are actually Pelagornithids which still persist in the warmer regions of the globe as the most parsimonuious hypothesis for some of those reports: but the creatures with a diamond-shaped body and long thin trailing tail has still got to be based on mistaken visual impressions of manta rays. It is also possible that some excited witnesses have confused sightings of the two different creatures. But Pelagornathids do not have tails and could not be construed as having such:
On the other hand, some birds like the Great blue herons do fly with their legs sticking straight out at back and looking like a long thin tail.
That makes three things that I have changed my mind on as better information came to me.
In case anybody is keeping track.