Very good Mike and Jackie, so why is that? When looking at objects (koi) underwater from ABOVE the water surface, the submerged odjects appear distorted, smaller or shorter. This phenomenon is called refraction or Fermat's principle.
In short, as a result of density changes, and light rays traveling between one point in air to another point in water, follow a path that is bent thus distorting the koi's appearance, depending on the depth and angle of fish. The same happens from the fish's perspective as well. They are equally shocked to see how big their master is when they are lifted out of the water the first time. LOL