Scaup:
Looks fairly good for male Scaup IMHO: no tuft, rounded head, black on bill restricted to nail and its immediate surrounds (cf. Advanced Bird ID Handbook P.23), bulkier than tufted with prominent chest, vermiculation on flanks, highest point of head on front of crown, head wholly dark and tertials wholly dark, scapulars grey flecked. I suppose concern could be lack of "bulk".
Decent head shape head-on thought perhaps could be heavier jowled but just OK I think.
Picture showing possibly more black on bill than I would like (angle doesn't help here)
and faint banding but juveniles tend to show "smudgy triangular dark tip but less sharp band than Tufted Duck" cf British Birds P.51 for details.