GPS without GPS may be doable with a boat because digital navigation charts are available and more reliable than those for roads.
Rather than GPS use radio detection gear to find bearing to local AM and FM radio stations whose broadcasting towers are all known locations. The computational power in any current computer would be more than enough to crunch the numbers and then show location on digital charts.
As a bonus the system would probably allow fantastic radio reception for entertainment and could also be used to locate and track ships emitting radar signals, giving the boat radar of a sort without being an emitter of radio signals itself.
I think you missed the entire point of the article. Americans shouldn’t have to tell the government where they are at all times. Are we have three people or not?
The accuracy of such a system is dubious - several degrees of uncertainty to the RF source. Especially if you don’t have line of site to it, i.e. over the horizon.
The system that this is likely discussing is also what commercial shipping, super yachts, and sailing boats use to announce themselves to others in the area. You can go dark - and get run over by the supertanker!