The Ocean Sciences Building at the University of Washington in Seattle is a brightly modern, four-story structure, with large glass windows reflecting the bay across the street.

On the afternoon of July 7, 2016, it was being slowly locked down.

Red lights began flashing at the entrances as students and faculty filed out under overcast skies. Eventually, just a handful of people remained inside, preparing to unleash one of the most destructive forces in the natural world: the crushing weight of about 2½ miles of ocean water.

In the building’s high-pressure testing facility, a black, pill-shaped capsule hung from a hoist on the ceiling. About 3 feet long, it was a scale model of a submersible called Cyclops 2, developed by a local startup called OceanGate. The company’s CEO, Stockton Rush, had cofounded the company in 2009 as a sort of submarine charter service, anticipating a growing need for commercial and research trips to the ocean floor. At first, Rush acquired older, steel-hulled subs for expeditions, but in 2013 OceanGate had begun designing what the company called “a revolutionary new manned submersible.” Among the sub’s innovations were its lightweight hull, which was built from carbon fiber and could accommodate more passengers than the spherical cabins traditionally used in deep-sea diving. By 2016, Rush’s dream was to take paying customers down to the most famous shipwreck of them all: the Titanic, 3,800 meters below the surface of the Atlantic Ocean.

Engineers carefully lowered the Cyclops 2 model into the testing tank nose-first, like a bomb being loaded into a silo, and then screwed on the tank’s 3,600-pound lid. Then they began pumping in water, increasing the pressure to mimic a submersible’s dive. If you’re hanging out at sea level, the weight of the atmosphere above you exerts 14.7 pounds per square inch (psi). The deeper you go, the stronger that pressure; at the Titanic’s depth, the pressure is about 6,500 psi. Soon, the pressure gauge on UW’s test tank read 1,000 psi, and it kept ticking up—2,000 psi, 5,000 psi. At about the 73-minute mark, as the pressure in the tank reached 6,500 psi, there was a sudden roar and the tank shuddered violently.

“I felt it in my body,” an OceanGate employee wrote in an email later that night. “The building rocked, and my ears rang for a long time.”

“Scared the shit out of everyone,” he added.

The model had imploded thousands of meters short of the safety margin OceanGate had designed for.

In the high-stakes, high-cost world of crewed submersibles, most engineering teams would have gone back to the drawing board, or at least ordered more models to test. Rush’s company didn’t do either of those things. Instead, within months, OceanGate began building a full-scale Cyclops 2 based on the imploded model. This submersible design, later renamed Titan, eventually made it down to the Titanic in 2021. It even returned to the site for expeditions the next two years. But nearly one year ago, on June 18, 2023, Titan dove to the infamous wreck and imploded, instantly killing all five people onboard, including Rush himself.