It's now thought the US navy detected sounds that signalled the catastrophic implosion of the Titan sub during its descent to the Titanic wreckage.
Multiple chunks of debris from the vessel have been found near the Titanic wreck site using a remote controlled underwater search vessel; confirming all five people onboard the submersible are dead.
Various experts have raised concerns about the Titan's design and contruction, including its carbon fiber and titanium hull.
Ron Allum is an Australian deep-sea engineer and explorer, who helped to design the submersible that filmaker James Cameron used to reach the deepest-known point of Earth's seabed in the Mariana Trench in 2012.
He says retrieving the debris or images of the Titan wreckage is essential to working out exactly what went wrong and stopping it happening again.
