How many atmospheres can this ship withstand?

Well it's a spaceship airplane, so I'd say anywhere between zero and one."

So his goal was to make a deep sea taxi of sorts. Rich guy affordable and capable of carrying more than 1 or 2 people at a time. Based on what I've read and seen he had two main reasons for the design:

1. Titanium/steel would've been too heavy and required a different design.
2. A sphere has too little volume to carry the number of passengers he wanted so he used a cylinder.

His use of CF was not only mostly untested but where it had been tried it was found lacking. It is strong in one direction but not others. The manufacturing process was very difficult and fraught with issues. Making such a large component that thick meant many many wrappings that had to be precisely done. For instance, they would get bulges that had to be reduced immediately or they'd amplify with more wrappings. So they would grind down those spots and wrap over them. The problem here is now you've broken the fibers and created end points and fracture initiation points. Things like the junction between the metal end caps and the CF tube were also an issue.

He was very cocky about how often you could reuse the vessel and tried to be cheap on testing which would involve sacrificing vessels. At 5,600 PSI small things that you could ignore in, say, an airplane structure, become wildly amplified.

Personally I didn't see the point of the whole trip except for bragging rights. You'd be watching most things on a monitor anyway and your porthole was this little, very thick, acrylic hole. You might as well send a robot down and watch on a screen on the ship.