The bit with the contract is @ 2:40:

An experimental submersible vessel that has not been approved or certified by any regulatory body and could result in physical injury, disability, emotional trauma or death.

There was some speculation the pressure vessel could have imploded, due to it being made out of thick fiber glass, which is like glass wherein any tiny imperfection under pressure can cause the entire vessel to break. This is why other pressure vessels are made out of stainless steel, they're easier to inspect.

If the vessel didn't implode, there's a decent chance it's floating on the surface, but lost. This is because the ballast for these subs is heavy metal attached via electromagnet. Should anything go wrong, the magnets can be disengaged, and the sub with resurface.

Here's hoping it's lost and can be found, imploding is a horrifying way to go, albeit a quick one.

And their navigation is dependent on text messages from the support ship they charter. Oh, dear.