Submerged submarines can't communicate by radio, except for receiving VLF/ELF transmissions.
As for ships on the surface, long-range radio propagation is due to the signal bouncing off of the ionosphere.
Is there a place (perhaps near the magnetic poles) where the ionosphere either is not there or does not reflect RF?
Just because it's stupid, futile and doomed to failure, that doesn't mean some officer won't try it.
-- R. Rather