They told us that our moving water was a loon. They'd seen it mentioned on the web, and come to take a look. Specifically, a red-throated loon (Gavia stellata). The boy shared his field glasses, and I lucked out and had them at the right moment, when the loon was above water. We stayed outside for a few minutes, wishing for better light (it was an overcast morning).
The sun came out about ten minutes later. We grabbed our cameras (and a set of field glasses, but I never took them out of their pouch). The light was a lot better, and the loon was spending more time above the surface. We walked around the edge of that bit of water, taking photos, a few of which came out reasonably well. I uploaded several of mine to Flickr. Here are three, cut to save your friends page.



Red-throated loons are less common than the common loon (which we saw one of in the park 15 years ago). Also, while New York is in their winter range, the summer range doesn't normally go south of Newfoundland and Manitoba.