When the US Coast Guard was asked about the chance of recovering the bodies of the five men aboard the Titan, it said there is an "incredibly unforgiving environment down there on the sea floor".
Experts say that the extreme force of the implosion means it would almost certainly be impossible.
The equivalent of the weight of the Eiffel Tower in Paris was resting on the submersible, explains Professor of Marine Autonomy Blair Thornton.
What protected the men from the ocean outside was the sub’s structure.
“Imagine now that the thing protecting you from those large forces disappears in an instant,” he says.
“In a rush of water, the force would be immense - around 10,000 tonnes dropping onto the structure,” he adds.
Denise Court, a professor of forensic genetics, says it would be very difficult to get to the area quickly enough to recover bodies.
But the huge implosion on the small submersible already means there is little hope of returning the victims to their loved ones, she says.
Titan mothership heads back to St John's from debris site
As we've been reporting, several vessels remain at the site of the debris field today in the aftermath of the likely implosion.
But the Polar Prince, the mothership of the Titan sub that launched it on Sunday, is heading back to St John's, Newfoundland, Canada.
It is expected to arrive there tomorrow morning.
Vessels at the wreck site are constantly moving around the area, but this map shows the position some of the ships involved with the search held this morning.
Horizon Arctic is a commercial vessel which operated the Palegic Odysseus 6K ROV - the craft which first found the debris field yesterday. The ship is operated by the same company which owns Polar Prince.
The map also highlights two other ships - French-operated L'Atalante, which has deployed the Victor 6000 ROV, and scientific research vessel John Cabot, which is operated by the Canadian Coast Guard.
BBCCopyright: BBC
Tycoon posts texts after turning down places on ill-fated sub
A Las Vegas businessman has revealed how he was offered two discounted places on the ill-fated Titan submersible but turned them down.
Three days ago Jay Bloom posted: "So this is crazy… I got invited to go on this dive. If I accepted, I would’ve been one of the five onboard right now."
Rush is believed to have died along with four others on the sub's latest dive to see the Titanic.
In the course of the text conversation, first reported by Mail Online, Bloom raises concerns over safety - prompted by his son Sean - but is reassured by Rush who writes: "There hasn't even been an injury in 35 years in a non-military sub."
Bloom says he also saw Rush in person in March, and they discussed the dive. Bloom says in his post: "He (Rush) was absolutely convinced that it was safer than crossing the street."
The Las Vegas tycoon goes on to pay tribute to those who lost their lives.
Jersey sub search equipment stood down
BBCCopyright: BBC
The equipment has now been removed from Jersey AirportImage caption: The equipment has now been removed from Jersey Airport
Specialist equipment bound for the North Atlantic sub search is being returned to the Guernsey business that owns it.
A Remotely Operated Vehicle (ROV) owned by Magellan was seen on Thursday, being prepped to load onto a US plane at Jersey Airport but plans were changed after it was confirmed all five passengers of the Titanic submersible had died.
In a statement, the firm said it was " deeply saddened by the news confirmed by the Unified Command yesterday" and extended its deepest condolences to the families and loved ones affected.
Marcus Sutton, managing director of Sutton Transport Services, said it had been tasked with removing the gear from the airport.
Waivers may not shield OceanGate from lawsuits - legal experts
Liability waivers signed by the five men on board the Titan may not shield OceanGate from potential lawsuits by their families, US legal experts tell Reuters news agency.
"If there were aspects of the design or construction of this vessel that were kept from the passengers or it was knowingly operated despite information that it was not suitable for this dive, that would absolutely go against the validity of the waiver," personal injury lawyer and maritime law expert Matthew Shaffer says.
Joseph Low, a personal injury lawyer from California, says: "There are so many different examples of what families might still have claims for despite the waivers, but until we know the cause we can't determine whether the waivers apply."
David Pogue, a reporter from CBS News, the BBC's partner in the US, made the trip with OceanGate last year and reported that the waiver he signed mentioned the possibility of death three times on the first page.
OceanGate could argue it was not grossly negligent and that the waivers apply because they fully described the inherent dangers of the dive, Reuters reports.
The degree of any potential negligence and how that might impact the applicability of the waivers will depend on the causes of the disaster, which are still under investigation.
Neither the BBC nor Reuters has seen the legal waivers the passengers were asked to agree.
'It's about warnings that were ignored' - Titanic director
More now from Titanic film director James Cameron who said he wishes he'd been more vocal about the OceanGate expedition before they set off.
He said the diving company, which specialises in submersibles for tourism, industry, research and exploration "shouldn't have been doing what it was doing" but he was "unaware that they weren't certified" because he wasn't really studying it.
Cameron compared the Titan tragedy to that of the Titanic, saying: "It's about warnings that were ignored."
He told Reuters: "That ship [Titanic] is lying at the bottom of the ocean, not because of its steel or the nature of its compartments, but just because of bad seamanship.
"The captain was warned, there were icebergs ahead, it was a moonless night and he ploughed ahead, for whatever reason."
He adds that now, at the same place, "there's one wreck lying next to the other wreck, for the same damn reason".
A recap of what's been happening
If you're just joining us this afternoon, tributes have been pouring in for the five passengers on board the Titan submersible who died after a suspected implosion.
There has also been criticism of OceanGate, the company which operated the sub - and a call to end trips to the Titanic wreck.
Here's your lunchtime recap of what has been happening over the past few hours:
The Dawood family, who have lost both Shahzada Dawood, 48, and his son Suleman, 19, says they are "overwhelmed with the love and support" they have received
The family of British billionaire explorer Hamish Harding has said he was a "dedicated father" and that "we lost him doing what he loved"
OceanGate, whose chief executive Stockton Rush also perished on board its Titan sub, said it was a "tragic time"
The company has come under criticism from experts in the field
Dik Barton, the first British man to dive to the wreck of the Titanic, called into question the design and maintenance of the sub, saying "there were many red flags flying here"
Sunak's thoughts with explorers' families after 'unimaginably difficult ordeal'
PA MediaCopyright: PA Media
UK Prime Minister Rishi Sunak has expressed his sadness at the deaths of the five people aboard the Titan submersible.
A Downing St spokesman says Sunak's "thoughts are very much with the loved ones of those who have died in this tragic incident" who have endured "an unimaginably difficult ordeal in the last few days".
He added that the Foreign, Commonwealth and Development Office was in touch with the families to provide support.
Deep sea tourism industry will grow - expert
ReutersCopyright: Reuters
Prof Stefan Williams says there may be calls for more regulationImage caption: Prof Stefan Williams says there may be calls for more regulation
Stefan Williams, professor of marine robotics at the University of Sydney, says he believes the commercial deep sea tourism industry will continue to grow despite the loss of the Titan submersible.
"I suspect
we will continue to see this industry grow," he tells Reuters.
"There may be calls for more
regulation, better understanding of how these sorts of vehicles are designed, built
and certified for use in these deep sea environments."
He says there has been a lot of discussion in the submersible community about the ethics using the Titanic wreck site as a tourist destination.
"This is a relatively new field with a relatively short history of trying to cater to that deep sea tourism industry, and this is the first tragedy of its nature."
Keen interest in 'exploring different natural habitats'
Engro Corporation and DH GroupCopyright: Engro Corporation and DH Group
Shahzada Dawood and his son Suleman were two of the five men who died on the Titan.Image caption: Shahzada Dawood and his son Suleman were two of the five men who died on the Titan.
Shahzada Dawood and his son Suleman were two of the five men who died on the Titan.
The Dawood family released a statement while the search for the vessel was under way in which they described Shahzada as a "loving father" with a keen interest in "photography, especially wildlife photography, and exploring different natural habitats".
From one of Pakistan's richest families, the British businessman was vice-chairman of Engro Corporation and the Dawood Hercules Corporation.
Suleman was a student at the University of Strathclyde where he had just completed his first year at the university's Business School.
Tributes to 'true explorer' Paul-Henri Nargeolet
ReutersCopyright: Reuters
Paul-Henri Nargeolet led the first expedition to the TitanicImage caption: Paul-Henri Nargeolet led the first expedition to the Titanic
RMS Titanic, Inc. has been collecting tributes from friends and admirers of "true explorer" Paul-Henri Nargeolet - one of five men killed on board the Titan sub.
Known affectionately as PH, and nicknamed Mr Titanic, he has appeared in several documentaries about the ship and has led expeditions to the wreck dozens of times.
"PH was a legendary figure in the world of Titanic," writes Rebecca, who adds: "His work has inspired so many people, myself included, and has allowed us to gain new perspectives of the disaster."
Susan says: "RIP Mr Nargeolet - may you discover the lengths, breadths and depths that heaven has to offer you. You will be missed."
Several who knew Nargeolet personally also shared their thoughts.
"The warmth and kindness he radiated was matched only by his seriousness and reverence about his work," writes Hans.
David, from Brazil, adds: "I am speechless, heartbroken. Rest in peace, our scientists and explorers."
Your comments on this story
We've been getting some readers' comments on the Titan submersible - as we're interested in seeing what people are saying about the tragedy in the north Atlantic.
Here is a selection sent into us at BBC News:
Quote Message: I think it's utterly disrespectful to commercialise visits to sites/locations that mark tragic moments for families. This is because it undermines the dignity of the dead, as in the case of Titan trip. The wreckage can be accessed with the view of learning lessons but definitely not for profit making. Governments must ban such activities." from Jonathan A Annan Erith, England
I think it's utterly disrespectful to commercialise visits to sites/locations that mark tragic moments for families. This is because it undermines the dignity of the dead, as in the case of Titan trip. The wreckage can be accessed with the view of learning lessons but definitely not for profit making. Governments must ban such activities."
Quote Message: I don't think it's right that so much advertising is made about the Titanic. The mystery of the Titanic should remain a secret. These five curious people paid for this curiosity with their lives. Let the souls in the Titanic finally sleep in peace." from Christine Stewart Collins Germany
I don't think it's right that so much advertising is made about the Titanic. The mystery of the Titanic should remain a secret. These five curious people paid for this curiosity with their lives. Let the souls in the Titanic finally sleep in peace."
Quote Message: Is there something very telling of the response to how five, extremely wealthy, volunteers met their fate in the bottom of the ocean, is completely different to how we respond to hundreds, if not thousands, of people die in the desperate pursuit to seek safety." from Rory Kenya
Is there something very telling of the response to how five, extremely wealthy, volunteers met their fate in the bottom of the ocean, is completely different to how we respond to hundreds, if not thousands, of people die in the desperate pursuit to seek safety."
Derbyshire man feared dangers of 2001 Titanic wreck trip
BBCCopyright: BBC
Peter Bailey, who visited the Titanic wreck in 2001, says he had been praying for the safe return of those on board OceanGate's Titan before receiving news of the tragedy.
Bailey, from Matlock, in Derbyshire, won a trip to see the wreck more than 20 years ago but the perils involved nearly put him off going.
The dangers of the journey two and a half miles under the ocean were "drilled into us from day one", he says.
It was made clear that even something like a hairline fracture that allowed water to seep in would result in instant death for all on board.
But he says he was glad to have undertaken the journey despite the danger, adding: "it will live with me for the rest of my life."
Time to 'consider seriously' ending human trips to Titanic - society chief
The president of the Titanic International Society says it is time to "consider seriously" whether human trips to the ship wreck should end "in the name of safety".
In a statement, Charlie Haas says the call is issued on the basis that there is "relatively little remaining to be learned from or about" the Titanic.
He also urges that an "extensive, detailed investigation by the US Coast Guard, the National Transportation Safety Board and/or their Canadian counterparts" be carried out into Titan's design.
"Additionally, intensive pre-service inspection of deep-sea submersibles should be required by international regulation," Haas says.
"Just as Titanic taught the world safety lessons, so, too, should Titan’s loss.
"Titanic also taught the world about the dangers of hubris and overreliance on technology. This expedition’s tragic ending has shown that these lessons remain to be learned."
The timeline of events of the Titan sub
We've been following the multinational search for the Titan over the last five days, but what led us to this point and how was the sub found? Here's the timeline:
17 June: Hamish Harding, who went on the submersible, tweeted that the mission was "likely to be the first and only manned mission to the Titanic in 2023" due to the worst winter in Newfoundland in 40 years
18 June: The Titan set off from the Polar Prince heading for the remains of the Titanic some 3,800m below the surface of the sea. The crew lost contact with the vessel around one hour and 45 minutes into the dive. They tweeted that a search had began
21 June: The US Coast Guard tweeted that a Canadian aircraft had detected underwater noises in the search area that resulted in remotely operated vehicle (ROV) operations exploring the noise
Ships in the North Atlantic continued to search and banging noises were discovered
22 June: Debris was discovered by an ROV near the Titanic wreck. The tail cone of the Titan was found 1,600 feet (488 metres) from the bow of the Titanic on the seafloor. Experts confirmed that the vessel had imploded
OceanGate released a statement confirming that CEO Stockton Rush, Shahzada Dawood and his son Suleman Dawood, Hamish Harding and Paul-Henri Nargeolet, had sadly died in the accident
Ex-Royal Navy captain considers causes of implosion
Former Royal Navy submarine captain Ryan Ramsay has outlined some possible reasons for the implosion of OceanGate's Titan on its descent towards the wreck of the Titanic.
Ramsay told the PA news agency that one of two things may have happened - the hatch with the 17 bolts used to seal the passengers in had failed, which caused the hull to collapse "because there's huge amounts of pressure, even halfway down".
Another possibility is that there was a prior defect in the pressure hull itself, leading to the same result, he added.
"The only positive out of it is that it was instantaneous and they didn't know anything," he said.
The latest on the Titan submersible
If you're just joining us this morning, officials have confirmed that the OceanGate Titan submersible is likely to have imploded during its descent, killing all five men on board.
Here's a recap of what we know so far:
Fragments of the Titan sub were located on the ocean floor yesterday, 480m (1600ft) from the bow of the Titanic wreck
The US Navy detected a sound consistent with an implosion just hours after Titan began its dive on Sunday, but the US Coast Guard says it's still not known when or where the implosion happened
Banging noises heard earlier this week have been attributed by experts to other ships in the area
The loopholes OceanGate exploited were unwise, says sub expert
Video content
Video caption: The loopholes OceanGate exploited were unwise - sub expertThe loopholes OceanGate exploited were unwise - sub expert
William Kohnen, chairman of the Manned Underwater Vehicles Committee, has told the BBC that regulations for building submersible vessels were "written in blood".
Kohnen wrote a letter raising safety concerns about OceanGate's development of Titan in 2018.
He says OceanGate circumvented certification processes by operating in international waters.
Which ships remain at the Titan debris site?
The US Coast Guard says some vessels are remaining at the site of the debris field before teams start being demobilised.
The Polar Prince, the mothership of the Titan sub that launched it on Sunday, is now returning to St John's, Newfoundland, Canada, and is expected to arrive there tomorrow morning.
Horizon Arctic is a commercial vessel which has operated the Palegic Odysseus 6K ROV, which found the debris field. The ship is operated by the same company which owns Polar Prince.
L’Atalante is a French-operated ship that has deployed the Victor 6000 ROV, which can operate at the depth of the Titanic wreckage site like the Odysseus 6K.
John Cabot is is a scientific research vessel with sonar search capabilities operated by the Canadian Coast Guard.
BBCCopyright: BBC
University is 'shocked and profoundly saddened' by student's death
ReutersCopyright: Reuters
The University of Strathclyde in Glasgow has paid tribute to its student Suleman who died in the Titan submersible alongside his father Shahzada and three others.
The university said in a statement that staff and students are "shocked and profoundly saddened by the death of Suleman Dawood and his father in this tragic incident".
Shahzada Dawood was a founding patron of Prince’s Trust International. The charity said it was deeply saddened by the tragedy and "valued [the Dawood family's] support
of our work in Pakistan for many years".
The British Asian Trust also paid tribute to Shahzada, describing him as a "wonderful and generous man who supported our work in South Asia for many
years" and his son Suleman as someone who was "just emerging into adulthood with a promising future
ahead".
Live Reporting
Brandon Livesay & Alex Binley
All times stated are UK
Get involved
Is there any chance of recovering the victims?
Georgina Rannard
Science reporter
When the US Coast Guard was asked about the chance of recovering the bodies of the five men aboard the Titan, it said there is an "incredibly unforgiving environment down there on the sea floor".
Experts say that the extreme force of the implosion means it would almost certainly be impossible.
The equivalent of the weight of the Eiffel Tower in Paris was resting on the submersible, explains Professor of Marine Autonomy Blair Thornton.
What protected the men from the ocean outside was the sub’s structure.
“Imagine now that the thing protecting you from those large forces disappears in an instant,” he says.
“In a rush of water, the force would be immense - around 10,000 tonnes dropping onto the structure,” he adds.
Denise Court, a professor of forensic genetics, says it would be very difficult to get to the area quickly enough to recover bodies.
But the huge implosion on the small submersible already means there is little hope of returning the victims to their loved ones, she says.
Titan mothership heads back to St John's from debris site
As we've been reporting, several vessels remain at the site of the debris field today in the aftermath of the likely implosion.
But the Polar Prince, the mothership of the Titan sub that launched it on Sunday, is heading back to St John's, Newfoundland, Canada.
It is expected to arrive there tomorrow morning.
Vessels at the wreck site are constantly moving around the area, but this map shows the position some of the ships involved with the search held this morning.
Horizon Arctic is a commercial vessel which operated the Palegic Odysseus 6K ROV - the craft which first found the debris field yesterday. The ship is operated by the same company which owns Polar Prince.
The map also highlights two other ships - French-operated L'Atalante, which has deployed the Victor 6000 ROV, and scientific research vessel John Cabot, which is operated by the Canadian Coast Guard.
Tycoon posts texts after turning down places on ill-fated sub
A Las Vegas businessman has revealed how he was offered two discounted places on the ill-fated Titan submersible but turned them down.
Three days ago Jay Bloom posted: "So this is crazy… I got invited to go on this dive. If I accepted, I would’ve been one of the five onboard right now."
Jay Bloom has since published screenshots of text messages between himself and Stockton Rush, the CEO of OceanGate.
Rush is believed to have died along with four others on the sub's latest dive to see the Titanic.
In the course of the text conversation, first reported by Mail Online, Bloom raises concerns over safety - prompted by his son Sean - but is reassured by Rush who writes: "There hasn't even been an injury in 35 years in a non-military sub."
Bloom says he also saw Rush in person in March, and they discussed the dive. Bloom says in his post: "He (Rush) was absolutely convinced that it was safer than crossing the street."
The Las Vegas tycoon goes on to pay tribute to those who lost their lives.
Jersey sub search equipment stood down
Specialist equipment bound for the North Atlantic sub search is being returned to the Guernsey business that owns it.
A Remotely Operated Vehicle (ROV) owned by Magellan was seen on Thursday, being prepped to load onto a US plane at Jersey Airport but plans were changed after it was confirmed all five passengers of the Titanic submersible had died.
In a statement, the firm said it was " deeply saddened by the news confirmed by the Unified Command yesterday" and extended its deepest condolences to the families and loved ones affected.
Marcus Sutton, managing director of Sutton Transport Services, said it had been tasked with removing the gear from the airport.
Read more here.
Waivers may not shield OceanGate from lawsuits - legal experts
Liability waivers signed by the five men on board the Titan may not shield OceanGate from potential lawsuits by their families, US legal experts tell Reuters news agency.
"If there were aspects of the design or construction of this vessel that were kept from the passengers or it was knowingly operated despite information that it was not suitable for this dive, that would absolutely go against the validity of the waiver," personal injury lawyer and maritime law expert Matthew Shaffer says.
Joseph Low, a personal injury lawyer from California, says: "There are so many different examples of what families might still have claims for despite the waivers, but until we know the cause we can't determine whether the waivers apply."
David Pogue, a reporter from CBS News, the BBC's partner in the US, made the trip with OceanGate last year and reported that the waiver he signed mentioned the possibility of death three times on the first page.
OceanGate could argue it was not grossly negligent and that the waivers apply because they fully described the inherent dangers of the dive, Reuters reports.
The degree of any potential negligence and how that might impact the applicability of the waivers will depend on the causes of the disaster, which are still under investigation.
Neither the BBC nor Reuters has seen the legal waivers the passengers were asked to agree.
'It's about warnings that were ignored' - Titanic director
More now from Titanic film director James Cameron who said he wishes he'd been more vocal about the OceanGate expedition before they set off.
He said the diving company, which specialises in submersibles for tourism, industry, research and exploration "shouldn't have been doing what it was doing" but he was "unaware that they weren't certified" because he wasn't really studying it.
Cameron compared the Titan tragedy to that of the Titanic, saying: "It's about warnings that were ignored."
He told Reuters: "That ship [Titanic] is lying at the bottom of the ocean, not because of its steel or the nature of its compartments, but just because of bad seamanship.
"The captain was warned, there were icebergs ahead, it was a moonless night and he ploughed ahead, for whatever reason."
He adds that now, at the same place, "there's one wreck lying next to the other wreck, for the same damn reason".
A recap of what's been happening
If you're just joining us this afternoon, tributes have been pouring in for the five passengers on board the Titan submersible who died after a suspected implosion.
There has also been criticism of OceanGate, the company which operated the sub - and a call to end trips to the Titanic wreck.
Here's your lunchtime recap of what has been happening over the past few hours:
Sunak's thoughts with explorers' families after 'unimaginably difficult ordeal'
UK Prime Minister Rishi Sunak has expressed his sadness at the deaths of the five people aboard the Titan submersible.
A Downing St spokesman says Sunak's "thoughts are very much with the loved ones of those who have died in this tragic incident" who have endured "an unimaginably difficult ordeal in the last few days".
He added that the Foreign, Commonwealth and Development Office was in touch with the families to provide support.
Deep sea tourism industry will grow - expert
Stefan Williams, professor of marine robotics at the University of Sydney, says he believes the commercial deep sea tourism industry will continue to grow despite the loss of the Titan submersible.
"I suspect we will continue to see this industry grow," he tells Reuters.
"There may be calls for more regulation, better understanding of how these sorts of vehicles are designed, built and certified for use in these deep sea environments."
He says there has been a lot of discussion in the submersible community about the ethics using the Titanic wreck site as a tourist destination.
"This is a relatively new field with a relatively short history of trying to cater to that deep sea tourism industry, and this is the first tragedy of its nature."
Keen interest in 'exploring different natural habitats'
Shahzada Dawood and his son Suleman were two of the five men who died on the Titan.
The Dawood family released a statement while the search for the vessel was under way in which they described Shahzada as a "loving father" with a keen interest in "photography, especially wildlife photography, and exploring different natural habitats".
From one of Pakistan's richest families, the British businessman was vice-chairman of Engro Corporation and the Dawood Hercules Corporation.
Suleman was a student at the University of Strathclyde where he had just completed his first year at the university's Business School.
Tributes to 'true explorer' Paul-Henri Nargeolet
RMS Titanic, Inc. has been collecting tributes from friends and admirers of "true explorer" Paul-Henri Nargeolet - one of five men killed on board the Titan sub.
Known affectionately as PH, and nicknamed Mr Titanic, he has appeared in several documentaries about the ship and has led expeditions to the wreck dozens of times.
"PH was a legendary figure in the world of Titanic," writes Rebecca, who adds: "His work has inspired so many people, myself included, and has allowed us to gain new perspectives of the disaster."
Susan says: "RIP Mr Nargeolet - may you discover the lengths, breadths and depths that heaven has to offer you. You will be missed."
Several who knew Nargeolet personally also shared their thoughts.
"The warmth and kindness he radiated was matched only by his seriousness and reverence about his work," writes Hans.
David, from Brazil, adds: "I am speechless, heartbroken. Rest in peace, our scientists and explorers."
Your comments on this story
We've been getting some readers' comments on the Titan submersible - as we're interested in seeing what people are saying about the tragedy in the north Atlantic.
Here is a selection sent into us at BBC News:
Derbyshire man feared dangers of 2001 Titanic wreck trip
Peter Bailey, who visited the Titanic wreck in 2001, says he had been praying for the safe return of those on board OceanGate's Titan before receiving news of the tragedy.
Bailey, from Matlock, in Derbyshire, won a trip to see the wreck more than 20 years ago but the perils involved nearly put him off going.
The dangers of the journey two and a half miles under the ocean were "drilled into us from day one", he says.
It was made clear that even something like a hairline fracture that allowed water to seep in would result in instant death for all on board.
But he says he was glad to have undertaken the journey despite the danger, adding: "it will live with me for the rest of my life."
Read the full story here.
Time to 'consider seriously' ending human trips to Titanic - society chief
The president of the Titanic International Society says it is time to "consider seriously" whether human trips to the ship wreck should end "in the name of safety".
In a statement, Charlie Haas says the call is issued on the basis that there is "relatively little remaining to be learned from or about" the Titanic.
He also urges that an "extensive, detailed investigation by the US Coast Guard, the National Transportation Safety Board and/or their Canadian counterparts" be carried out into Titan's design.
"Additionally, intensive pre-service inspection of deep-sea submersibles should be required by international regulation," Haas says.
"Just as Titanic taught the world safety lessons, so, too, should Titan’s loss.
"Titanic also taught the world about the dangers of hubris and overreliance on technology. This expedition’s tragic ending has shown that these lessons remain to be learned."
The timeline of events of the Titan sub
We've been following the multinational search for the Titan over the last five days, but what led us to this point and how was the sub found? Here's the timeline:
Ex-Royal Navy captain considers causes of implosion
Former Royal Navy submarine captain Ryan Ramsay has outlined some possible reasons for the implosion of OceanGate's Titan on its descent towards the wreck of the Titanic.
Ramsay told the PA news agency that one of two things may have happened - the hatch with the 17 bolts used to seal the passengers in had failed, which caused the hull to collapse "because there's huge amounts of pressure, even halfway down".
Another possibility is that there was a prior defect in the pressure hull itself, leading to the same result, he added.
"The only positive out of it is that it was instantaneous and they didn't know anything," he said.
The latest on the Titan submersible
If you're just joining us this morning, officials have confirmed that the OceanGate Titan submersible is likely to have imploded during its descent, killing all five men on board.
Here's a recap of what we know so far:
The loopholes OceanGate exploited were unwise, says sub expert
Video content
William Kohnen, chairman of the Manned Underwater Vehicles Committee, has told the BBC that regulations for building submersible vessels were "written in blood".
Kohnen wrote a letter raising safety concerns about OceanGate's development of Titan in 2018.
He says OceanGate circumvented certification processes by operating in international waters.
Which ships remain at the Titan debris site?
The US Coast Guard says some vessels are remaining at the site of the debris field before teams start being demobilised.
The Polar Prince, the mothership of the Titan sub that launched it on Sunday, is now returning to St John's, Newfoundland, Canada, and is expected to arrive there tomorrow morning.
Horizon Arctic is a commercial vessel which has operated the Palegic Odysseus 6K ROV, which found the debris field. The ship is operated by the same company which owns Polar Prince.
L’Atalante is a French-operated ship that has deployed the Victor 6000 ROV, which can operate at the depth of the Titanic wreckage site like the Odysseus 6K.
John Cabot is is a scientific research vessel with sonar search capabilities operated by the Canadian Coast Guard.
University is 'shocked and profoundly saddened' by student's death
The University of Strathclyde in Glasgow has paid tribute to its student Suleman who died in the Titan submersible alongside his father Shahzada and three others.
The university said in a statement that staff and students are "shocked and profoundly saddened by the death of Suleman Dawood and his father in this tragic incident".
Shahzada Dawood was a founding patron of Prince’s Trust International. The charity said it was deeply saddened by the tragedy and "valued [the Dawood family's] support of our work in Pakistan for many years".
The British Asian Trust also paid tribute to Shahzada, describing him as a "wonderful and generous man who supported our work in South Asia for many years" and his son Suleman as someone who was "just emerging into adulthood with a promising future ahead".