Losing GPS in many circumstances isn't the end of the world...the Russians have been clobbering the signal over large chunks of the north eastern Mediterranean (usually to the north east of Cyprus) for some years but it's been perfectly possible to fly through that airspace without getting lost.
FWIW in the (large) aircraft case GPS is only one several devices that provide position information to the navigation system (others are usually ground based radio beacons and a system called inertial navigation)....so if GPS breaks or gets denied it's really not the end of the world, the system reverts to using one of the other (usually slightly less accurate than GPS) inputs as it's primary source for navigation...The only consequence if that happens is that in bad weather you cannot fly into some airports that only have instrument approaches predicated on having GPS working.
Don't know much about floating stuff but I know some larger ships ( and certainly some boats 
) have inertial navigation and radio inputs as well as GPS as part of the navigation suite so short term at least GPS outage shouldn't be a major problem for them.
OTOH anybody navigating solely by reference to GPS (e.g. a simple hand held commercial receiver) might have problems in low visibility.