It was low tide and the rocks just above the waterline were slick, causing McCann to remark on the wisdom of New York State rules against trespassing on riprap. He spotted an oyster scar, the whitish stain left by a shell, like a ghost bicycle by the roadside. “It’s stressful for an oyster in the intertidal zone in New York City,” he said, speculating that a parasite might have killed this one in its infancy. The breakwater was only a year old. Then he found another possible culprit: an “oyster drill”—a small snail with shell-penetrating teeth and a proboscis for slurping mollusk meat. He handed it to the windsurfer, who recalled childhood afternoons spent sending hermit crabs on “vacations,” but then thought better of airing out his old pitching arm on unsteady feet.