The crew onboard the ill-fated Titan submersible that imploded last year likely suffered overwhelming “terror and mental anguish” in their final moments because they “were well aware they were going to die,” a new lawsuit alleges.

The family of French explorer Paul-Henri Nargeolet slapped the $50 million wrongful death lawsuit on the sub’s operator, OceanGate, on Tuesday, accusing the company of gross negligence given the “doomed” vessel’s “troubled history.”

Nargeolet, 77, was one of five people aboard the Titan submersible when it suddenly imploded en route to the famed wreck site at the bottom of the North Atlantic in June 2023 — sparking a widespread probe into how the disaster occurred.

According to the suit, the submersible “dropped weights” just 90 minutes into its dive, indicating the crew had aborted or attempted to abort the dive early on.

“While the exact cause of failure may never be determined, experts agree that the Titan’s crew would have realized exactly what was happening,” the court papers charge.

“Common sense dictates that the crew were well aware they were going to die, before dying.”

The filing goes on to speculate on the horrific final moments Nargeolet and the four others onboard likely experienced after realizing their looming fate.

“The crew may well have heard the carbon fiber’s crackling noise grow more intense as the weight of the water pressed on Titan’s hull. The crew lost communications and perhaps power as well,” the suit said.

“By experts’ reckoning, they would have continued to descend, in full knowledge of the vessel’s irreversible failures, experiencing terror and mental anguish prior to the Titan ultimately imploding.”

In filing the lawsuit, Nargeolet’s family accused OceanGate of failing to disclose key facts about the vessel and its durability prior to the expedition.

“The lawsuit further alleges that even though Nargeolet had been designated by OceanGate to be a member of the crew of the vessel, many of the particulars about the vessel’s flaws and shortcomings were not disclosed and were purposely concealed,” lawyers for his estate said in a statement.

Nargeolet, affectionately dubbed “Mr. Titanic,” had taken more than three dozen trips to the liner’s wreck before boarding the ill-fated OceanGate submersible — including the very first human expedition to visit the site back in 1987.

Nargeolet, who was a director of underwater research for RMS Titanic, was a seasoned veteran and wouldn’t have participated in the Titan expedition if OceanGate had been more transparent, the suit argues.

“Decedent Nargeolet may have died doing what he loved to do, but his death — and the deaths of the other Titan crew members — was wrongful,” the lawsuit alleges.

A spokesperson for OceanGate declined to comment on the suit. It must respond to the complaint in the coming weeks, court papers state.

The Titan submersible had set off the morning of June 18, 2023, but lost contact with its support vessel roughly two hours later.

The wreckage was later found on the ocean floor about 984 feet from the Titanic.

In addition to Nargeolet, the implosion killed OceanGate CEO and co-founder Stockton Rush, British adventurer Hamish Harding, and Pakistani father and son Shahzada and Suleman Dawood.

With Post wires