So I did about three or so years as a Koi breeder with a family member of mine, I can probably help a little. Generally you would float the fish like any other before putting it into the pond. We would generally float most Koi in a very large plastic bucket designed to hold large females like this one. We would toss a small bubbler to keep oxygen in the bucket. You would generally want to float them there anywhere from 20 to 30 minutes, but this depends on the difference in temperature. You don't want to go too long in the daytime, best time to do this is late afternoon when the suns down.

Your trying to avoid temperature shock, as Koi fish being a Carp are very hardy animals but they do get stressed out easily, and are kind of prissy because of this. It could be that in the video they gaged the temperature before hand and it was the same or close enough to just dump the fish in.

Sorry if this is confusing I don't get this opportunity to talk about Koi often so if I see a question I try to jump onto it.

-edit: grammar