Dirk took a bearing with a compass on his wrist, then slipped his regulator between his teeth and expelled a burst of air from his BC. Sinking a few feet below the surface, he gently began kicking toward the massive covered dock. The corrugated tin structure was relatively narrow, offering just a few feet of leeway for the ship occupying the lone berth. Yet the dock was well over a football field long, easily accommodating the ninety-meter tanker.

The luminescent dial of the compass was barely visible in the inky water as Dirk followed his set bearing. The water grew lighter from the shoreside lights as he approached the dock entrance. He continued swimming until the dark shape of the tanker’s hull loomed before him. Slowly ascending, he broke the surface almost directly beneath the tanker’s stern rail. He quickly scanned the nearby dock, finding it deserted at the late hour. Pulling his hood away from one ear, he listened for voices, but the drone of the pump house would have made a shout difficult to detect. Gently kicking away from the side of the ship, he tried to get a better look at the vessel.

Though a large ship from Dirk’s perspective, she was tiny as far as LNG carriers go. Designed with a streamlined deck, she could carry twenty-fi ve hundred cubic meters of liquefied natural gas in two horizontal metallic tanks belowdecks. Built for coastal transport duty, she was dwarfed by the large oceangoing carriers that could hold more than fifty times the amount of liquefied natural gas.

The ship was probably ten or twelve years old, Dirk gauged, showing wear at the seams but judiciously maintained. He didn’t know what modifications had been made for the ship to carry liquid CO2 but presumed they were minor. Though CO2 was somewhat denser than LNG, it required less temperature and pressure extremes to reach a liquid state. He peered up at the name Chichuyaa , beaded in gold lettering across the stern, noting the home registry of Panama City painted in white lettering below.

A rise of bubbles rippled the water a few yards away, then Summer’s head popped through the surface. She glanced at the ship and dock, then nodded at her brother as she pulled out a vial and collected a water sample. When she finished, Dirk pointed toward the bow and dropped back beneath the surface. Summer followed suit, tracking her brother as he swam forward. Following the dark outline of the tanker’s hull, they swam down the length of the ship, quietly surfacing off the ship’s bow. Dirk eyed the tanker’s Plimsoll line a few feet overhead, noting that the vessel was just a foot or two shy of its fully loaded displacement.