The family of a French explorer who died in a submersible implosion has filed a more than $50 million lawsuit, saying the crew experienced “terror and mental anguish” before the disaster and accusing the sub’s operator of gross negligence.

Paul-Henri Nargeolet was among five people who died when the Titan submersible implodedduring a voyage to the famed Titanic wreck site in the North Atlantic in June 2023. No one survived the trip aboard the experimental submersible owned by OceanGate, a company in Washington state that has since suspended operations.