Titanic sub: Avatar director James Cameron slams OceanGate Expeditions for ignoring repeated warnings over safety

Titanic director James Cameron has lashed out at the owners of the Titan submersible, saying they ignored repeated pleas from within the diving community over safety fears.

The five people on the Titan submersible are all believed to be dead following what the US Coast Guard said was a "catastrophic implosion".

Investigations are underway to figure out exactly what happened to the Titan submarine after large pieces of debris were found near the Titanic wreck on the ocean floor.

Speaking to ABC News for the first time since the news of the missing sub, Cameron - who has made 33 dives to the wreck of the Titanic - said the loss of lives had been "the nightmare we've all had to live with".

"Many people in the community were very concerned about this sub and a number of the top players in the deep submbergence community even wrote letters to the company saying that what they were doing was too experimental to carry passengers and it needed to be certified," he said.

"I'm struck by the similarity of the Titanic disaster itself, where the captain was repeatedly warned about ice ahead of his ship and yet he steamed at full speed into an ice field on a moonless night and many people died as a result.

"So it's a very similar tragedy where warnings went unheeded - and to take place at the same exact site, with all the diving that's going on all around the world, I think is just astonishing. I think it's really quite surreal."

Cameron also revealed he personally knew the fifth man onboard, Paul-Henry Nargeolet. The 77-year-old former French navy diver and renowned explorer was a friend who Cameron had got to know through the diving community and while working on his own submersible to head to the Titanic's wreck.

"For him to have died tragically in this way is almost impossible for me to process," Cameron told ABC News.

Cameron has spoken before about the dozens of deep sea dives he has made in submersibles.

In 2012, he dived to the Mariana Trench, considered one of the deepest spots in the Earth's oceans at almost seven miles below the surface, in a 24-foot submersible vehicle he designed called the Deepsea Challenger.