I agree that it would be useful to see more photos. I don't have experience with Semipalmated, but the bird on these photos looks to me very like Red-necked Stint, especially the long-bodied and 'hunch-backed' appearance. I would have expected semipalmated to appear a bit more like Little Stint, with a slightly more upright posture. Possibly also a slightly deeper base to the bill. In my opinion the definition in the photos is not enough to show conclusively whether the toes are webbed or whether this is an illusion from the photograph. Red-necked Stint is a very variable species in terms of plumage (especially at this time of year), and of course behaviour can also vary individually. Of course, semipalmated sandpiper is a possibility, but I think higher resolution pictures to conclusively show the webbing or the pattern of any breeding plumage feathers would help to resolve this question.
