'I gave him my seat.' Christine Dawood on losing her husband and son on the Titanic sub.

Christine Dawood was supposed to be on the submersible with her husband, Shahzada, when it left for its voyage to the Titanic wreck earlier this month.

Her son, Suleman, was initially "so disappointed" he couldn't accompany them to the 1912 wreck because he wasn't old enough at the time.

But when COVID-19 saw their plans delayed to this year, the mother-of-two decided to give her seat to the now 19-year-old.

"I stepped back and gave them space to set [Suleman] up, because he really wanted to go," Christine told the BBC in her first interview after losing her husband and son during the expedition. 

Suleman wanted to solve the Rubik's Cube underwater in an attempt to break a world record. 

"He said, 'I'm going to solve the Rubik's Cube 3,700 metres below sea at the Titanic' and he was so excited about this." 

"I was really happy for them because both of them, they really wanted to do that for a very long time," she said, as she recalled that she "hugged and joked" with the pair before they set off on the expedition which coincided with Father's Day in the US. 

Suleman Dawood (left) and his father Shahzada (right) were among those on board the sub. Image: AAP/Facebook.

Then came the devastating news. 

"The sentence 'we lost com'. I think that will be a sentence I never want to hear in my life again," she recalled.

Christine and her daughter, Alina, were on board the sub's support vessel, the Polar Prince, when they were told communications had been lost with the Titan submersible.

"I didn't comprehend at that moment what it meant – and then it just went downhill from there," she said.

"We all thought they are just going to come up so that shock was delayed by about 10 hours or so... we were constantly looking at the surface."

It wasn't until four days in, that hope started to fade. 

"I think I lost hope when we passed the 96 hours mark," she said. 

"That’s when I even sent a message to my family onshore. I said, 'I’m preparing for the worst'."

She said Alina clung on to hope for her father and brother a bit longer. 

"She didn't lose hope until the call with Coast Guard, when they basically informed us that they found debris."

Suleman and Shahzada were among the five passengers who lost their lives in the sub, including Oceangate CEO Stockton Rush, British billionaire Hamish Harding, and Titanic expert Paul-Henri Nargeolet. 

The family held a funeral prayer for Shahzada and Suleman on Sunday. 

Christine said she intends to continue with her husband's work and she and her daughter have vowed to try to learn to finish the Rubik's Cube in Suleman's honour.

"That's going to be a challenge for us because we are really bad at it but we are going to learn it," she said.

In a statement to People last week, the Dawood family paid tribute to the father and son. 

"The relationship between Shahzada and Suleman was a joy to behold; they were each other's greatest supporters and cherished a shared passion for adventure and exploration of all the world had to offer them," the statement read. 

The US Coast Guard is leading an international investigation into the loss of the submersible. 

When asked how she would "begin to get closure," Christine questioned "Is there such a thing? I don't know."

"I miss them," she said. "I really, really miss them."

- With AAP. 

Feature Image: BBC/AAP/Facebook.