After taking part in survey Training for the Snow Plover survey, I learned that this bird, the Sanderling, is one of the birds that people often mistake for Snow Plovers.
Seen on their own, I see why as they appear so much smaller than the other common beach birds like Turnstones, etc. However, once you see them in comparison to an actual Snowy, you realize that Sanderlings are quite a bit larger.
Also, they are much more gray/white where the Snowy's have a touch of light brown.
Both can have partial black shoulder marks...more or less defined depending on whether it's breeding season or not.
Some other key differences are behavioral...
...Sanderlings are more likely to be found running almost ceaselessly between the waves and the tide line on the beach.
When roosting in groups, Sanderlings require less "personal space" between birds than do Snowy's.
Everyone occasionally experiences itchy feathers, though.