If the plane is relatively intact, how does a remote sub get a black box out?
I actually don’t know, but it’s been done before, so they obviously have some approach that works.
It would be tough. In an F-16, the FDR is bolted to the frame of the aircraft by for four hex head fasteners.
The sub would have to have the ability to unscrew the fasteners with the properly sized driver.
Also, the wiring harness would need to be uncoupled or cut.
I don’t have any experience with CVR’s but the procedure would likely be similar.
Especially at 18,000 feet deep