I think I've seen pictures of this type of thing for use with irrigation channels: like a giant spoon that pivots on a post, with a weight opposite the bowl. Still unclear how the return motion with no water isn't just as hard as lifting water with no counterbalance.

Here it is, the shadoof! https://en.wikipedia.org/wiki/Shadoof

Doesn't seem to explain though. "The bucket can be lowered by the operator using their own weight to push it down; the counterweight then raises the full bucket without effort." So then, raise the water using your own weight, don't bother with the counterweight? Oh, I suppose the point is to have a bucket of water conveniently stationary at shoulder height, but held only tenuously in place when it's empty in the depths of a well, rather than the other way round. Right.