By mcrosbie - Apr 30 10:32 pm
You may be correct, but the photo doesn't show inconclusive markers. The bill would be one such indicator - length, colour and shape.
I just photographed a number of RB Mergansers recently and the bird in your photo looks different. I have seen PB Grebes in the ocean, but uncommonly.
However, if you wish to use my photos to help with your IDs, then click on the Albums heading on my Flickr account and you will see a mostly alphabetical list of species. Click on the Red-breasted Merganser Album and you will see a number of photos of this species (male and female) taken during different seasons. Ditto with the Grebes, etc.