I feel like there are many more innovative, horrific ways to die in an underwater submersible that haven't been fully explored yet. Besides being crushed to death by the ocean, there's also:

• Slowly running out of oxygen after the submersible gets stuck on something somewhere

• Freezing to death after the power gets knocked out and can't be restored from the inside

• Dying to smoke inhalation after something in the cabin ignites

• Springing a small leak and not being able to do anything as the air leaks out of the cabin and you drown

• Springing a major leak and watching someone get ripped in half by the pressure of the water, then drowning

• Experiencing any of the above in a cramped tube that isn't big enough to stand in and is no bigger than a king sized bed

Also very important for billionaires to continue bolting themselves in from the outside so they can't escape without outside assistance, that's totally a good idea that can never go hilariously wrong and they should keep doing it.