The chick scrambled onto the nest from somewhere else, after I had been watching them for some time. The chick is too old to have been born in this nest. It later became apparent that this chick seemed attached to this coot, but the adult was one of a pair, the other of the pair also having a single coot in tow. This was also odd; if there was to be a second brood, why not use the (presumably) existing nest. Why was the chick using this new nest. The chick spent half its time, when the adult approached, helping build the nest; and half eating the new nesting material. Again this lasted some time.
Eventually the juvenile left for elsewhere. Throughout all this time the adult was industriously building, plaiting reeds into the structure. Two days later, the activity was still the same, except that the nest had become detached from the post and was floating some distance away.