The lawsuit, seeking more than $50 million in damages, accuses the sub's operator, OceanGate, of gross negligence.

Nargeolet was one of the five individuals who tragically lost their lives when the Titan submersible imploded during a voyage to the famed Titanic wreck site in the North Atlantic in June 2023. This experimental submersible, owned by OceanGate, was known for its troubled history and has led to the company suspending its operations.

Attorneys representing Nargeolet's estate, from the Buzbee Law Firm of Houston, Texas, have alleged that OceanGate failed to disclose crucial information about the vessel's flaws and shortcomings, which ultimately contributed to the tragedy. They claim that despite Nargeolet being designated as a crew member, many significant details about the submersible were intentionally concealed.

OceanGate declined to comment on the lawsuit, which was filed on Tuesday in King County, Washington. Tony Buzbee, one of the attorneys involved, emphasized that one of the objectives of the lawsuit is to uncover the truth behind the incident and hold all responsible parties accountable.

Following the disaster, concerns regarding the Titan's unconventional design and its creator's refusal to undergo independent checks arose. The submersible's implosion prompted questions about the reliability and future of private deep-sea exploration.

In response to the incident, the US Coast Guard initiated a high-level investigation, which is currently ongoing. A significant public hearing related to this investigation is scheduled for September.

The ill-fated Titan made its final dive on a Sunday morning, June 18, 2023. Contact with the support vessel was lost approximately two hours later. After an extensive search and rescue mission, the wreckage of the Titan was discovered on the ocean floor, around 984 feet (300 meters) off the bow of the Titanic. The location of the wreckage was approximately 435 miles (700 kilometers) south of St. John's, Newfoundland.

Notably, Stockton Rush, CEO and co-founder of OceanGate, was operating the Titan when the implosion occurred. Alongside Nargeolet, British adventurer Hamish Harding and members of a prominent Pakistani family, Shahzada Dawood and his son Suleman Dawood, also lost their lives.

In the midst of this tragedy, RMS Titanic Inc., the company that owns the salvage rights to the Titanic, has recently undertaken its first voyage to the wreckage site in years. Last month, the Georgia-based firm launched its expedition from Providence, Rhode Island, marking a significant milestone in deep-sea exploration.

Paul-Henri Nargeolet, who served as the director of underwater research for RMS Titanic, was a seasoned veteran of underwater exploration. His estate's attorneys assert that he would not have participated in the ill-fated Titan expedition had OceanGate been more transparent about the submersible's capabilities and safety measures.

As the legal battle unfolds, the family of Paul-Henri Nargeolet hopes to find answers about the circumstances surrounding his untimely death and seeks justice for their beloved explorer who dedicated his life to unravelling the mysteries of the Titanic.