A dated video tour of the inside of Titan - the submersible that is missing near the Titanic ruins - demonstrates how restricted the five passengers onboard are in terms of space.
The very small vessel has no seats, one miniature bathroom, and moved around via "video game controller."
Passengers must sit on the floor, according to a BBC video from 2022 featuring OceanGate CEO Stockton Rush as he shows the inside of the submersible, The Mirror reports.
Read More: Missing Titanic submersible LIVE updates as underwater noises detected offering fresh hope
Rush is shown sitting on the ground during the tour - highlighting that there is not that much room around.
It has a small bathroom, one overhead light, a few wall lights, and a window. It is controlled using a video game controller that Rush holds up in the air during the tour.
The trip typically last eight hours from start to finish.
Three days have elapsed since Hamish Harding, Stockton Rush, Paul-Henry Nargeolet, Shahzada Dawood and his son Suleman lost communication during a deep-sea dive that they had each paid $250,000 to undertake.
Mike Reiss, who joined OceanGate to glimpse the deteriorating wreck in 2022, said the trip is less tourism than it is true exploration.
"You sign a massive waiver that lists one way after another that you could die on the trip, they mention death three times on page one. So it's never far from your mind. As I was getting on to the sub, that was my thought: That this could be the end," he told the BBC this week.
David Pogue, a correspondent for CBS Sunday Morning, told the public in an interview that when he went last year for a tour as a member of the press, he "couldn't help noticing how many pieces of this sub seem improvised."
According to CEO Rush, Titan is special as it is one of the few underwater vessels like this that includes a private toilet for customers at the front of the sub. A small curtain is pulled across when it is in use, and the pilot turns up some onboard music.
The company's website states "you restrict your diet before and during the dive to reduce the likelihood that you will need to use the facilities," though.
Someone attempting to stand up inside would find it difficult.
Wall-mounted lamps are the only light source, and the sub has heat as the ocean is freezing. There is no word on how long those would last, considering the sub only has 96 hours of oxygen.
OceanGate concedes the vessel contain lots of "off-the-shelf technology," which "helped to streamline the construction and makes it simple to operate and replace parts in the field."
Four years ago, the company explained why the Titan had not been classed by an independent body. "Bringing an outside entity up to speed on every innovation before it is put into real-world testing is anathema to rapid innovation," it said.
In a promotional video, OceanGate Expeditions software security expert Aaron Newman tells prospective clients that travelling on the sub is "not a ride at Disney, you know".
"There's a lot of real risk involved, and there's a lot of challenges," he says.
