Its depressing news. Maybe they're alive sitting on the bottom and can't surface or maybe they're caught in a net. Its happened before.
I like visiting submarines when I go on road trips. Most of the time its a WW2 fleet boat but I have seen the Trieste.
https://en.wikipedia.org/wiki/Trieste_(bathyscaphe)
The Trieste is old. The pressure hull is a welded titanium sphere. Buoyancy is controlled by a combination of tanks full of gasoline and some kind of lead or steel shot ballast.
If you run into a problem and want to get to the surface you release the shot and up you go. The gasoline tanks see sea pressure. Gasoline is lighter than seawater but is incompressible since it is a liqued.
Why this guy wanted to reinvent the wheel is beyond me.