The deep-sea submersible that conquered the world's five deepest ocean trenches

History · Published 3 October 2026 Swipe more like this →

In short: Commissioned by explorer Victor Vescovo for $37 million, the Limiting Factor became the first crewed vessel to reach the deepest point in all five oceans. Now renamed Bakunawa, this titanium-hulled marvel continues to push the boundaries of marine exploration, capable of withstanding pressures far beyond the ocean's deepest known depths.

Built by Triton Submarines, the Limiting Factor was designed for the Five Deeps Expedition, a mission launched in 2018 to visit and map the deepest points of the world's five oceans. The vessel features a spherical titanium pressure hull, 90 mm thick, engineered to withstand pressures of 14,000 msw—a safety margin that significantly exceeds the 11,000-meter depth of the Challenger Deep. Its unique design allows for three-axis movement, optimized for the long vertical descents and ascents required to reach the hadal zone.

The submersible's operational history is marked by significant scientific and historical milestones. During the Five Deeps Expedition, it reached the bottom of the Puerto Rico Trench in December 2018 and the South Sandwich Trench in February 2019. By April 2019, it had descended to the Challenger Deep, setting a world record depth of 10,928 meters. Beyond exploration, the vehicle has been used to identify deep-sea wrecks, including the USS Johnston and the RMS Titanic, and to conduct biological sampling that has revealed previously unknown species.

In 2022, the vessel was sold to Gabe Newell’s research organization, Inkfish, and renamed Bakunawa, after a creature from Filipino mythology. The craft remains a pinnacle of engineering, featuring a seven-function hydraulic manipulator arm and an emergency life support system rated for 96 hours. Its name originally served as a tribute to the sapient warship in Iain M. Banks' Culture series, reflecting the ambition of its creators to navigate the most inaccessible environments on Earth.

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