Its not the pressure, but the fact water blocks radio waves. Submarines can’t get GPS signals or transmit their location. Submarines have to rely on other means such as IMUs to track their own location.
They have locator beacons size of a thermos (that ping powerfully using particular frequencies) which they fit on flights etc... i believe some can be received a couple miles+ down in good conditions like are seeing now.
But clearly not everything sinks, or the sub would never be able to surface. If it's just a matter of engineering work, that's kind of literally their job.