A mission specialist for the company that owned the Titan submersible has spoken about the last time she saw its doomed passengers as they left to explore the wreck of the Titanic.

“I saw five people smiling on the way to their journey,” Renata Rojas told a US Coast Guard inquiry on Thursday. “They were just happy to go, that’s the memory I have.”

Titan, operated by OceanGate, imploded in June 2023 during the dive, killing all on board. Ms Rojas, who was on a surface support vessel, said everything was “working very smoothly” before the sub began its descent.

But she told the probe that she remembered losing communications, asking colleagues: “We haven’t heard from them, where are they?”

The Titan’s implosion led to questions over the submersible’s safety and design, and the materials used in its construction.

Ms Rojas told the inquiry that she was the “platform assistant” on the day of the dive, “mostly standing around until somebody needed help”.

The inquiry earlier this week was told of the last messages as the sub descended towards the Titanic, with the crew stating “all good here” minutes before the sub suffered a catastrophic implosion.

Ms Rojas said she was on the bridge of her vessel as communications were lost, but said rescue protocol advised to wait an hour as passengers might be spending extra time exploring their destination.

The conversation then turned as the sub failed to resurface. Ms Rojas said she recalled conversations on the bridge about calling the coast guard.

“We went into ‘go mode’,” she said.

She said there were a number of options available if the sub was stuck on the ocean floor, including releasing the legs or waiting for the tide to change. The Titan had 96 hours of life support onboard, she added.

However, she said there was nothing anyone in the sub could have done if the hull failed.

Ms Rojas described a 2021 expedition in which she recalled how the dome fell off the submersible as it was being retrieved from the water.

At one point when the submersible was being pulled back onto the ship, she described a “seesaw” effect where the sub was supposed to be gently placed on the ship, but the crew let it go and it fell.

Ms Rojas said the forces on the front platform of the sub sheared the clamp and the dome broke vacuum.

“There was only, I think, two bolts or four bolts on the dome,” she said.

“It started dripping, falling off,” she added. The incident led to crews putting 18 bolts on the dome for other expeditions.

Rojas, a self-described Titanic obsessive, told the inquiry she never felt unsafe during her own dives.

“I found them to be very transparent about everything,” she said about OceanGate staff debriefs. “I knew the risk and still decided to go.”

The inquiry continues.