Sorry to say but there in fact maybe very little you can do.
“Float” is the one word description and suits but A LOT more will be needed to somehow get the nuance across.
To use the word, “Float like a butterfly, sting like a bee.” IF you don’t “get” it, sounds impossible on a few levels…relating back to the athlete, some would take that phrase and paralysis by analysis ensues, others would say, “I don’t get it…” and just sort of quite trying to understand etc.
The parallel in my mind is the concept of “space” being taught to team sport athletes (soccer is a good example since the space is so large, relatively speaking compared to say ice hockey or basketball, though it applies to all IMO).
To start with it is a difficult concept to verbally explain so it may take 100x ways or attempts just for one athlete (and, of course, it helps if this is done, more or less, one on one partially for that exact reason). Telling a soccer player they need to be so and so far from a teammate is not the same “thing”.
It is also similar, IMO (again) to trying to tell someone to be “in the zone”, sorry, from all I have read, it is very, very difficult if not impossible, to just put yourself in the “zone” but once you have been there, in fact the more often you have been there, the “easier” it is to get there again.
Try not to get discouraged but also don’t set yourself an impossible task, high school maybe a bit young for such a “high level” concept.
[I am by no means saying high schoolers can not “get it” just that athletes a bit more mature will more likely have a bit better chance of at least understanding what is desired. I keep reading that being in such a place (the “zone” or in this case, “floating”) is not happenstance but for me as a coach it has always been very much “chance” (for better or worse, I am “known” for asking athletes to duplicate what they just did since it was what was after and even that is a tough ask…)