Since 2019, the company has offered tourists the chance to explore the Titanic’s wreckage more than 2 miles below the ocean’s surface off the coast of Canada — at $250,000 per ticket.

It is a rare souvenir from a milestone event in the Titanic story — and now it could be the ticket to an absolute fortune. A pass for the launch of the ill-fated liner in Belfast on May 31 ...