Goosanders, they look a bit like a cross between a grebe and a duck, actually nest in holes in trees. Often high off the floor. I am guessing this was their first day out of the nest. When I saw them, they had to have had just come down a long length of very fast moving river, full of rapids and white water. The waves easily larger than them.
I think she was taking them a quarter of a mile or so, downstream, which is calmer.
