Mum, is our nest supposed to be floating?

Our elusive moorhen has been hiding out for some weeks now on the edge of the pond island. She darts under cover whenever she sees me approaching, so catching an image of her is quite a feat! No sign of any chicks so far this year, but when there were trout in the pond, they discovered they had an insatiable appetite for trout pellets, and would come running out of the water to greet me when I shook the can for the trout's food. I wonder if Mum is one of those chicks returned to her birthplace...