Titanic tour submersible goes missing, wealthy British and others on board.

A U.S. submersible on a sightseeing tour to see the wreckage of the British-Australian passenger ship Titanic, which sank after striking an iceberg in 1912, has gone missing. U.S. and Canadian authorities have been searching for the submersible by deploying underwater sonar and other means, but no one has been able to locate it. The submersible had on board experts as well as a wealthy British man and others.

According to the U.S. Coast Guard, which held a press conference in Boston on April 20, the submersible had about 40 hours of oxygen remaining as of 1 p.m. on the same day.

The tour is operated by Ocean Gate, an undersea exploration company based in Washington State. According to Reuters, the company runs a five-week tour every summer, with each participant paying $250,000 (about 35 million yen).

On board the submersible are Ocean Gate founder and CEO Stockton Rush and French exploration expert Paul-Henri Narjolais, known as "Mr. Titanic. Also reportedly on board are Hamish Harding, a wealthy British businessman, and Shahzada Dawood, a Pakistani businesswoman of British nationality, and her son.

The missing submersible was scheduled to visit the wreckage of the Titanic in the Atlantic Ocean for two and a half hours, and lost contact with the boat one hour and 45 minutes after it began diving on the 18th. Ocean Gate posted on Twitter on the 19th, "We are mobilizing all resources for the return of the crew.

Search operations have been hampered by strong currents and other obstacles. According to U.S. media, submarine officials had previously warned of serious safety concerns over the tour.