A Koi sock is made to capture and move Koi without damaging it. There are two versions: The blue Japanese Koi transport sock is partially waterproof, allowing you to move the Koi with water and all. The meshes at the end of the sock allow you to easily drain the water.

With this sock you can also scoop water from the pond to quickly fill a Koi bowl, for example. The black koisok is completely permeable to water.
You scoop the Koi out of the pond and all the water drains away, making lifting a large Koi easy.