Clock ticking for missing Titanic tourist submarine in Atlantic Ocean

Search teams are racing against the clock to find a tourist submarine that went missing during a visit to the Titanic's wreckage.

Five people were reportedly onboard, including French and British nationals, the submersible that vanished in the deep waters of the Atlantic Ocean on Sunday.  

They had four days worth of oxygen left at most, as of Monday afternoon. 

The Joint Rescue Coordination Centre in Halifax, Nova Scotia said the vessel was reported overdue around 9:13 p.m. Sunday, about 700 kilometres south of St. John’s, Newfoundland. 

Lt. Cmdr. Len Hickey said a Canadian Coast Guard vessel and military aircraft were assisting the search effort, which was being led by the US Coast Guard in Boston.

OceanGate Expeditions, which runs the Titanic tour, confirmed its submersible was missing. 

“We are deeply thankful for the extensive assistance we have received from several government agencies and deep sea companies in our efforts to reestablish contact,” the company said in a statement. 

“We are working toward the safe return of the crewmembers.”

Ocean Gate reportedly charges €230,000 per passenger for the trip to the Titanic wreck, which lasts eight days and descends to a depth of 3,800m. 

British businessman Hamish Harding, CEO of the company "Action Aviation", recently indicated on Instagram he would be on the vessel. 

"The submarine's crew is made up of some legendary explorers, some of whom have completed more than 30 dives on the RMS Titanic since the 1980s," he wrote in the post on Saturday. 

French explorer Paul-Henry Nargeolet, Pakistani businessman Shahzada Dawood and his son Suleman are also thought to be onboard, alongside Stockton Rush, chief executive of OceanGate. 

The Titanic wreck lies 3,800 metres down at the bottom