Good job on this, Richard. I also feel the bird is a Harlequin. I finally got to see the bird after sunset in poor light and no chance for a photo even though the bird swam by me at 15 meters. The petite size and rounded head shape that I observed in my bins made an immediate connection to Harlequin. I wish I could have taken some photos as nice as yours!

Nice that our paths have crossed several times in the past few days!

Best,

Ed Harper