By Nicholas Bogel-Burroughs / © 2024 The New York Times Company

Coast Guard investigators detailed a series of problems Monday that took place in the years before the Titan submersible imploded deep in the ocean, including testing oversights and equipment failures, as they sought to learn more about the catastrophe that killed five people last year.

The investigators revealed that the Titan had experienced dozens of problems during previous expeditions, including 70 equipment issues in 2021 and 48 more in 2022, including dying batteries.

In part of the winter before the fatal crash in June 2023, the investigators said, the Titan was stored unprotected in bitterly cold temperatures outside a facility in Newfoundland with no protection from the elements.

Then, less than four weeks before the fatal mission, the craft was found “partially sunk” two days after a test, following a night of high seas and fog. And a few days before it imploded, five people in the Titan were slammed against its wall as it was resurfacing from a mission.

The vessel’s troubled development history was detailed as the U.S. Coast Guard’s Marine Board of Investigation convened in South Carolina for its first public hearing on the disaster, an attempt to begin answering the question of what went wrong on the vessel’s mission to visit the Titanic shipwreck.

A transcript of the final communications from the vessel indicated that the crew may have tried in the moments before the disaster to abandon the trip and resurface. The crew told the vessel’s support ship in a final message that the Titan had dropped two of the weights that were helping it descend. Still, investigators said, no transmissions “indicated trouble or any emergency.”

When the submersible’s crew sent its last communication, it was more than 2 miles below the surface of the Atlantic Ocean. The crew was not heard from again.

Exactly what led to the implosion has been the subject of an inquiry by the Coast Guard for more than a year. But much of that work has taken place out of view, with few new disclosures about what went wrong. Monday’s public proceeding began with an overview of the investigation and an animation of the submersible that illustrated what investigators had learned so far.

The investigators noted that the outside of the Titan’s hull was covered in polyurethane, which made it impossible to inspect the hull visually. And they said the hull had never been pressure tested up to industry standards.

The Marine Board of Investigation called the first of two dozen witnesses who are expected to testify over the next two weeks. Among them are former employees of OceanGate, the underwater exploration company that operated the submersible, and safety and marine experts who have insight into what caused the fatal event. The board is also likely to discuss evidence it has already gathered, including details about the Titan’s design and the company’s safety guidelines.

The biggest question for investigators is what caused the Titan to implode, an answer that is crucial to preventing any future accidents. They will specifically try to determine if there were flaws in the design of the submersible or the materials it was built with.

The CEO of OceanGate, Stockton Rush, who died in the implosion, was warned years earlier by submersible and ocean experts that his methods were still experimental and could have devastating results.

Since the accident, experts have noted several design decisions that may have saved the company money but meant that the submersible differed from others that had proved safe. Among them were the pill-like shape of the Titan’s hull — a sphere has been the industry standard — and the use of carbon fiber rather than titanium for the hull.

At a news conference Sunday, Jason Neubauer, a retired Coast Guard captain who is the chair of the board investigating the Titan, said his team had been working for 15 months to understand what had happened. He said the hearing Monday, in North Charleston, South Carolina, would be crucial for investigators to learn more about the disaster and to outline their findings so far.

“These proceedings are not just a formality,” he said. “They are a critical step in our missions to understand the contributing factors that led to the incident, and, even more important, the actions needed to prevent a similar occurrence.”

Neubauer said the investigation was one of the most complex he had ever participated in, partly because the implosion took place far out in the Atlantic Ocean, making it more difficult to gather the physical remnants of the destroyed craft.

Responding to a reporter’s question, he said that any potential evidence of criminal negligence would be passed on to the U.S. Justice Department.

The Titan submersible disappeared June 18, 2023, when it lost communication with its support ship after dropping into the water about 400 miles off the coast of Newfoundland, Canada. On board were Rush; Shahzada Dawood, a British Pakistani businessperson; Dawood’s 19-year-old son, Suleman; Hamish Harding, a British aviation tycoon and explorer; and Paul-Henri Nargeolet, a French maritime expert and leading authority on the Titanic who had visited the wreckage dozens of times before.

Nargeolet’s family filed a lawsuit against OceanGate last month, saying that the company’s CEO had misled Nargeolet about the craft’s safety. OceanGate suspended commercial and exploratory operations in the wake of the accident.

Four days after the submersible vanished, wreckage from the craft was found about a third of a mile from the front end of the Titanic. Months later, divers found human remains among debris.

This article originally appeared in The New York Times.