I suspect it was exciting for planes and boats when during the gulf war, the govt shut down GPS without warning.
There was no widespread commercial or recreational use of GPS during the Gulf War (August 1990 to Feb 1991). The government did not shut down GPS, they shut down the Selective Averaging, which made the GPS less accurate, because there were a very limited number of military units. Some military being deployed were able to get one of the few portable GPS units which were just being made for recreational boating. Having SA off allowed these units to be as accurate as the military grade GPS.
I was going to Australia to sail along the Eastern coast and my friend had an "in" with Micrologic. They had just released their first recreational boat fixed GPS unit (only 19 satellites up then--14 when the Gulf War started). I picked up the unit about a week before we were to fly down. By the day I left they had updated the unit to software 6, and I hooked it up to my car battery on the way to the airport to be sure it was working properly.
We did a couple of days experimenting. I was below with the GPS and a chart. The owner was on deck steering with his chart and compass, plus depth sounder and visual. I called the course, blind, and we ended up with in 100' of where I had predicted from the GPS. It was magic! I had used Loran C, A, Omega, VOR, Sat Nav (decent fix about every 6 hours on an average). None of these held a candle to the GPS!
Other ways of navigation before the modern era was using the lighthouse beacon and timing the electronic signal on long wave radio (302 khz), with the synchronized Fog horn to give distance off. The RDF gave you a bearing to the lighthouse, and the time delay gave you the distance off, by accounting for the speed of sound. In So. Calif. There were 4 light houses broadcasting on the same frequency, but they each broadcast their call letter in Morris Code so you could differentiate the light house. Pt Loma:
_._. I, Los Angeles:
._ _ II etc
Another way of navigation was using the depth finder. For example Redando Canyon leads right into King Harbor. One would plot a series of depths, often crossed with RDF bearings of either the lighthouses or radio stations in S. Calif. on a paper chart to determine a line of position.
I did a lot of coastal sailing in fog. Sound was very important--and one of the advantages of a sail boat in the Los Angeles area. I always made certain I had a good and very loud air horn-- not a wimpy little can of compressed air.. One became skilled at knowing the sound made by fishing seiners from the water taxi or Catalina Steamers--vs a large merchant ship...no radar, no GPS..
The OP did the correct procedure to continue dead slow, using all of the sensory input and electric equipment which he had available.