I can see you are having some fun and achieving good results with your new camera and long lens.
If at all possible, try to get as close to water level as you can when photographing species
such as grebe, ducks and merganser. Sometimes its just too dangerous to get down low,
especially during the winter when ice becomes an issue. I carry a folded piece of exercise
mat under my back pack so that I can whip it out whenever I need to sit on the ground.
Leaning backwards allows my backpack to support me. While not actual water-level the
seated station does give more satisfying water shots. Fully prone is even better but that
can be difficult even though I try to do my own stunts on set.