someone said that he most likely is going for air. I accepted that for a
minute as I will admit that he does this pretty much all the time, but then
thought "wouldn't that make him a mammal like a whale?" I don't mean to
appear dumb - but who is right? Bugs or air?

Koi do this when there is not enough dissolved oxygen in the water. It is
a sign you are not moving enough water through your pond.

Your pump should be 2500GPH or more. How big is your pump? What's its
source? What's its destination?

C//