Most electronics are not easily crushed
But a few must be protected
Resistors, ceramic caps, and most IC's actually handle 10,000 PSI or more without issue. Just keep them in clean mineral oil and they will usually handle the pressure.
Laser diodes, electrolytic caps, and quartz crystals however need protection.
While changing O-rings on this telemetry system housing, you can see the SFP laser modules that are kept under a Titanium dome. The rest of the electronics are simply helt ina thin housing filled with mineral oil.
This is a huge cost savings over placing the whole board in a sealed housing rated to thousand of meters deep.
If you need to modify your electronics to handle the deep ocean, please get in touch, as we have spent 2 decades doing this.