What has six legs and no head?

It was the end of an afternoon on the Semiahmoo beach. The tide was still going out, but we were cold and hungry and heading home. Squinting against the slanting light, watching for herons, I noticed three somethings; I couldn't make out what at that distance. Something silhouetted against the brightness, bigger than gulls, fatter than herons ... what was it?

It was too far to go see, too late. The camera serves as eyes, in cases like this. With the lens at its maximum, a hand more or less shading it, I got this photo.

Something missing.

I see, plain as day, walking along the water's edge, three people. Half-people, more accurately. Two women, one taller man, probably. Hard to tell for sure without a torso and head.

Zombies, out for a constitutional? What else walks around missing essential body parts?