The abandoned submersible Blue Cube lies in the Eastern Pool of Challenger Deep, almost eleven kilometres below sea level.
The seafloor is far from the lifeless plain that most expect. The crushing depths are home to a menagerie of piezophilic creatures that, ironically, humans describe as alien. The water column is thick with amphipods, tiny crustaceans that scavenge marine snow. Worms and holothurians live and feed on the soft sediment, gulping the mud down one end and spinning it out in spirals from the other. Single-celled not-quite-animals that scientists call xenophyophores form strange aggregates like the ruins of tiny desert cities.
In this deepest reach of the Pacific Ocean, humans too have made their mark, in the name of research and exploration. Ever since the first terrestrial visitors arrived in the sixties, the seafloor has accumulated a matrix of cables, cut tethers, military hydrophones, and discarded ballasts from scientific exploits.
The Deep has its landmarks. They are used as navigational aids by visitors. In the Eastern Pool is the Spider’s Web, a vertical crisscrossing of yellow aramid-coated fibre optic cables. Northwards are the remains of an imploded two-person submersible half-buried in the sediment. Somewhere near the very deepest point is a large rock, host to a veritable garden of anemones, but hadal biology holds little interest for the nameless collective of tourists with only one goal: descend to the deepest point, and then ascend alive. Most of them succeed.
One visitor was a Silicon Valley tech billionaire who had made his fortune in disposable power banks and cryptocurrency. He had seen Antarctica, climbed Everest, and floated in zero gravity. Challenger Deep was his final frontier. He had the money, but no legitimate research organisations would take him. Even the World Ocean Hadal Research Institution had long ago abandoned the Mariana Trench after losing multiple remotely operated vehicles to its depths.
Previous tourists had built their subs in partnership with various motor, watch, and aeronautics conglomerates, each claiming to push the boundaries of science and technology. But the sub design was always the same: an untethered titanium case engulfed in syntactic foam that made it positively buoyant without the ballast—crucial to the ascent. The tech billionaire went with a popular sports drink company. Within a year, they constructed a full-ocean-depth rated cube capable of withstanding over 1100 atmospheres of hydrostatic pressure. The thick walls were made of a top secret proprietary composite with gaps between the hull and the viewport to account for compression. The sports drink company painted the cuboid submersible their signature shade of isotonic blue and filled the seat pockets with cans of caffeinated electrolyte beverage.
The support ship was the tech billionaire’s own megayacht, repurposed with an A-frame for the mission. She steamed across the Pacific with Blue Cube on deck, and the weather was fine. The tech billionaire, in his sponsor-branded insulated boiler suit, climbed into the hatch. The support team calculated Blue Cube’s release from the ship perfectly and dropped the line.
The descent was a passive process driven by nothing but the sub’s negative buoyancy. It took four hours to hit the bottom. When the cube landed, it disturbed a cloud of sediment that took a long time to settle.
The team kept contact with the tech billionaire on the acoustic telemetry as he activated Blue Cube’s thrusters and inched his way deeper into the Eastern Pool. He spent an hour or so piloting Blue Cube around the trench. He took note of the rock formations and amphipods in the water column and prepared lines about the resilience of life for the press conference. He located the Spider’s Web and the imploded submersible, and he relayed their coordinates to his team, who were then able to triangulate his position and guide him to the very deepest point.
It was a seamless dive, until the thrusters appeared to be losing power. The tech billionaire assumed that the reserves were running low, meaning it was time to make his ascent. He’d seen all there was to see. He activated the ballast release that would drop the iron weight attached to the bottom of Blue Cube, and he waited to be shot back up to the surface.
Nothing happened.
He pinged the telemetry to let his support team know he was still alive before he tried again. And again.
Nothing.
He activated the rear cameras and, with some manoeuvring, managed to identify the problem: a taut line of fibre optic tether across the screen. It wasn’t difficult to figure out that the release mechanism was tangled.
He tried it again.
The onboard telemetry pinged to the ship for ninety-six hours after the failure, leaving the tech billionaire to die six fathoms directly below his megayacht. It is hard to say whether he perished from asphyxiation or cold.
Blue Cube became another landmark with which subsequent tourists triangulated their position. Some got close enough to catch a glimpse of the pilot’s mummified face. There were vague plans for retrieval in the upper echelons of wealthy self-described explorers, but these were swiftly abandoned when a new space tourism company opened its waitlist. Now Blue Cube is a grave that draws fewer mourners with every passing year. Discarded ballast weights are slowly swallowed by the sediment. No-longer-buoyant plastic bags come here to die, drifting like the spirits of jellyfish. The water carves nanoplastics out of microplastics, and the amphipods eat the pieces. On the edge of Blue Cube’s viewport, a ghostly white Galatheanthemum attaches itself to the titanium with its pedal disc. Its tentacles sway gently in the currents.