Remi said, “Come down with me. I think I’ve found another hearth. Bring the camera.”

Sam pulled himself up over the gunwale to reach the underwater camera, and they submerged again. Remi seemed to lose herself in the work. She led him to the stone hearth and let him examine it while she took the camera and photographed the site from every angle to record the positions of the potsherds around it. He watched the graceful movements of her body—in her wet suit looking a bit like her own shadow—and noticed a thin wisp of auburn hair had escaped from the hood of her suit at her forehead. He caught her bright green eyes looking at him through the glass of her mask, so he forced himself to relinquish the sight of her and look at the ring of charred stones she had uncovered beneath the sand. Then they filled their net bags carefully to bring more pottery up to be catalogued and mapped the site where they found them.

Suddenly Sam and Remi both heard the buzzing sound of a propeller. It grew louder, and as they looked up they saw the underside of a black hull speeding toward the anchored dive boat, throwing waves to each side. They could see the outdrive and propeller and the long spiral trail of churned bubbles behind it.

They watched the dive boat’s hull rock and saw the anchor chain tighten to hold it, tugging against the anchor they’d sunk into the sand and then going slack when the other boat slowed down and idled within a yard of theirs. In a minute or two, the black hull sped up again and moved away at high speed, bouncing as it crested each wave.

Sam pointed upward, and the two floated to the surface. Remi climbed the ladder, and Sam followed. As they took off their gear, Remi said, “Well? That was a little closer, wasn’t it? I’m glad we didn’t surface just as they came roaring in.”

She could see Sam’s jaw was working. “I think they zoomed in to look at what we’ve been bringing up from the bottom.”

“I hope they got a good look,” she said. “I don’t want to get chewed up by a propeller over a few potsherds and a middenful of thousand-year-old clamshells.”

“Let’s see who they are,” he said. He started the engine and stepped to the bow. Remi took the wheel and inched them forward in the direction of the anchor so its two flukes would be pulled forward and freed from the sand. Sam pulled the anchor up and stowed it under the foredeck. Remi brought the boat around so Sam could scoop up the small ring buoy that held the diver-alert flag, red with a white diagonal stripe, and pull in its light anchor, then stow both in the stern.

She pushed the throttle forward and accelerated in the direction of the Grand Isle Harbor.

Sam moved forward to stand beside Remi and rest his elbows on the roof of the cabin while he held the binoculars and scanned the horizon. As they sped along the coast, Remi’s long auburn hair whipped behind her in the wind. Sam said, “I don’t see their boat. They must have put into the harbor. We may as well head in too.”