A British billionaire explorer is on board the missing Titanic tourist submarine somewhere in the depths of the Atlantic Ocean.

Hamish Harding, who has previously travelled on the Challenger Deep to the bottom of the ocean, took to Facebook on Saturday to announce that he was joining OceanGate Expeditions for its Titanic mission this week.

Rachel Sharp reports:

The US Coast Guard tweeted that some of their crew is currently searching for an “overdue Canadian research submarine” approximately 900 miles from Cape Code, Massachusettes.

The Titanic shipwreck is located approximately 1,000 miles from Cape Cod in the North Atlanic Ocean.

A former British Navy officer has warned that the “timescale” of the missing Titanic submersible is “very concerning” – as it emerged that there has been no sign of life from the vessel for the past seven hours.

Former Rear Admiral Chris Parry told Sky News that the OceanGate Expeditions vessel could have fallen foul of a “catastrophic failure” or even have become tangled up in the debris of the famed shipwreck.

“It’s very concerning indeed,” he said.

“Having listened to the timescale it’s very worrying.”

Read the full story here:

OceanGate Expeditions uses Elon Musk’s Starlink to maintain communications while out in the ocean, the company revealed last month.

“Despite being in the middle of the North Atlantic, we have the internet connection we need to make our #Titanic dive operations a success - thank you @Starlink!” the company tweeted.

In September, The Independent’s Sheila Flynn spoke to Renata Rojas about how she finally ended up visiting the famed Titanic wreck at its underwater grave after a near lifelong obsession – and what the surreal journey was actually like.

Read the interview here:

OceanGates Expeditions offers tourist trips down to the Titanic wreckage at a cost of $250,000.

The cost covers training and an eight-day deep sea expedition to visit the wreckage.

The submersible fits five people and can reach depths of 4,000 metres.

The company describes the trip as a “chance to step outside of everyday life and discover something truly extraordinary”.

OceanGate Expeditions offers trips for tourists at a cost of around $250,000.

Last year, CEO Stockton Rush told CBC that the subs can hold up to five people.

“Titan is the only five-person sub capable of going to the Titanic depth, which is half the depth of the ocean,” he said.

“There’s no switches and things to bump into, we have one button to turn it on. Everything else is done with touch screens and computers, and so you really become part of the vehicle and everybody gets to know everyone pretty well.”

The crew on board the missing submarine have made no contact with dry land for the past 7 hours, according to Sky News.

The submersible operates by being launched from a mother ship which then later recovers it at the end of its mission.

It usually sends signals to its mother ship every 15 minutes.

But, no signals have been received for more than seven hours.