The gas mixture they breathed contained less oxygen than air, the rest made up mostly of helium, an inert gas that doesn’t have the narcotic effect that the nitrogen in air does. But helium is also a “cold” gas, meaning that the body loses heat faster through respiration than with air. Tusker again cursed his decision not to wear a thicker suit. The temperature reading on his dive computer said 67 degrees, a full 20 degrees colder than at the surface. Tusker was used to cold water from his wreck diving in the Great Lakes, but there he wore insulation layers and a drysuit. For the ten-minute bottom time on the Vampire, he’d be fine, but he’d suffer on the long deco hang. So be it.

The anchor had hooked on the bow railing. Tusker had forgotten to account for this possibility. It meant a 100-yard swim to the aft end of the ship where the hole in the hull was, and then back again so they could ascend on the anchor line. This round trip would take up almost their entire planned bottom time. He gestured to Sam along the hull in the direction they needed to swim and set off in a measured flutter kick. Overexertion meant becoming hypoxic or using up their gas. In the thin beams of their twin torches, the swim felt interminable and disorienting, like walking in a railway tunnel lit only by a flashlight. Tusker paused every few kicks to make sure Sam was at his side. They were like two astronauts, spacewalking untethered away from their craft.

After five minutes, the hull below their torch beams curved down and away slightly as they approached the stern end of the shipwreck. The hole would come into view any moment now. There! Tusker shouted through his regulator and gestured. Sam nodded. He exhaled slightly, causing a decrease in his buoyancy, and descended towards the wound in the ship. He reached up and pressed the button to turn on the small GoPro camera he had secured to his harness, and confirmed that the red light was blinking.

Tusker ran his hand along the edge of the opening. It was blackened and jagged. There was no sign of an explosion or collision, just a neatly traced rectangle, clearly made by a cutting torch. He turned to make eye contact with Sam and held out his palm to tell her to stay put. She nodded. Tusker contorted his body upright and descended into the hole, fins first. The opening was big enough, but with the two smaller cylinders slung at his sides, it was an awkward move.