Female Long-Tailed Duck (maybe)

This is not a species with which I am familiar. It was on freshwater - Gaddon Loch (near Collessie, Fife) this afternoon. It was rather distant so has been greatly cropped but I'm sure it is clear enough for an ID.

I am hoping that I am correct with my tentative ID of a female long-tailed duck (Clangula hyemalis).

If so, they are more usually seen in a marine environment.

It kept diving under water - usually just as I focussed on it but managed two or three shots of it. This was the best.