A former employee warned company executives about the inefficiency of their hull design and the company's testing methods.

The ABC series takes a closer look at the submersible that went on a quest to see the wreckage of the Titanic and ended in tragedy.

The Titanic has intrigued the public from the moment it tragically crashed into an iceberg in the Atlantic Ocean and sank on April 15, 1912.

OceanGate said it is suspending all exploration and commercial operations after five people were killed during its expedition to the Titanic wreckage last month.

OceanGate said it is suspending all exploration and commercial operations after five people were killed during its expedition to the Titanic wreckage.

Debris recovered from the submersible that catastrophically imploded while on a voyage to see the Titanic wreckage last week contained "presumed human remains," the U.S. Coast Guard said.

Debris from the submersible that catastrophically imploded while on a voyage to see the Titanic wreckage last week was brought ashore Wednesday morning.

Pieces of the Titan vessel were unloaded from the Canadian Coast Guard pier in St. John's, Newfoundland.

A visual timeline recounting the events that led up to the disappearance of the Titan submersible.

While the recovery operation and investigation remains ongoing, here's what we know about the situation and how it unfolded.

Investigators said they are speaking with more people connected to the deadly Titan submersible incident as more victims' families speak out about their grief.

The U.S. Coast Guard has formed a marine board of investigation, working alongside the FBI and international agencies to get answers after the submersible tragedy last week.

Karl Stanley, a submersible expert, says he warned of safety flaws when he took a trip on the Titan submersible in 2019.

The Canadian ship that launched the Titan submersible arrived in Newfoundland as international investigators search for answers.

Investigators search for clues in the deadly implosion of the Titan sub, including voice recorders abord the launch ship that could hold new answers.

The U.S. Coast Guard on Saturday is taking the lead on the investigation into the loss of the craft and the five people on board.

Liability waivers "are not automatically enforceable," one expert said of a potential case against the submersible company.

Authorities are looking into what may have caused the likely catastrophic implosion that led to the deaths of all five passengers on board OceanGate's Titan submersible.

The Navy used a Cold-War-era sonar system to detect and locate the sound's origin.

Titan victims' deaths ‘brought the world together,’ uncle says.

The company behind the missing Titanic tourist submersible exaggerated the details of the industry partnerships behind its titan submersible.

The Coast Guard policy is not to ask for a refund from private operators.

Guillermo Söhnlein says those that participated in their expeditions were treated as "key members of the crew."

Here's what we know about the crew of the OceanGate sub.

The Oscar-winning "Titanic" director and the ocean explorer who discovered the Titanic wreckage both share their thoughts on the tragic implosion of the tourist submersible.

U.S. Coast Guard officials said debris from the submersible was found about 1,600 feet from the bow of the Titanic on Thursday morning, indicating a "catastrophic implosion."

The U.S. Coast Guard is now saying a “catastrophic implosion” destroyed the missing sub, taking the lives of the five people on board.

The director of “Titanic” said “many people in the community were very concerned” about the Titan submersible.

The U.S. Coast Guard said Thursday the submersible likely suffered a "catastrophic implosion" after debris was located 1,600 feet from the wreckage of the Titanic.

James Cameron has compared the tragic loss of the submersible Titan to the very thing that may have led the Titanic to its own demise.

ABC News’ Phil Lipof spoke with “Titanic” film director James Cameron and Robert Ballard, the first person to locate the Titanic wreckage, as the search for the missing sub comes to a tragic end.

The film director and longtime deep-sea diver and Bob Ballard, the man who first discovered the Titanic wreckage, speak with Whit Johnson.

After days of searching the ocean depths, rescuers confirmed they found debris of the tourist submersible and said the five passengers lost their lives.

The five-person submersible suffered an implosion, a Coast Guard official said.

Despite their onboard oxygen tank expected to be depleted sometime Thursday morning, the five people aboard the lost Titanic tourist sub could survive for hours.

Dr. Richard Moon is a former director of the Divers Alert Network, a nonprofit dedicated to improving SCUBA diving safety and a professor of anesthesiology.

Director James Cameron, and deep-sea explorer Robert Ballard discuss the presumed death of all aboard a submersible vehicle that went missing near the wreckage of the Titanic.

ABC News contributors and correspondents break down the presumed deaths of all five passengers aboard a submersible that went missing after a dive near the wreckage of the Titanic.

U.S. Coast Guard officials conceded crews are facing a daunting investigation to determine what caused the Titan submersible to implode underwater.

Five people, including the CEO of OceanGate, were aboard the sub when it imploded.

The five passengers aboard the missing submersible near the Titanic wreckage are presumed dead, according to Admiral John Mauger.

OcenaGat founder and CEO Stockton Rush is among the passengers on the missing vessel.

ABC News’ Jaclyn Lee and National Geographic's Kristin Romey break down why the search for the missing sub near the wreckage of the Titanic has become more desperate.

The U.S. Coast Guard announced via Twitter that "a debris field was discovered within the search area near the Titanic" wreckage.

That amount of breathable air is forecast to run out on Thursday morning.

The deadline comes as a U.S. Navy salvage system has arrived on an island off Canada’s Atlantic Coast to aid in the search and rescue efforts.

The submersible reported missing miles off the coast of Cape Cod was an unorthodox vessel with a relatively unproven history, according to company materials and experts.

Search and rescue teams are scrambling to locate the Titan submersible to rescue the five people onboard before time runs out.

ABC News’ Phil Lipof spoke with National Geographic editor Kristin Romey about the search for the missing deep-sea vessel as only hours remain before oxygen runs out.

As crews scour the Atlantic for the missing submersible, the Coast Guard said it's searching the area where an underwater noise was detected.