> I do wonder though if sailing the ship is basically a full-time job in itself

Someone should always be on watch if possible. It doesnt always happen as people do solo voyages. Open ocean most vessels would have transponders but if you're anywhere coastal you couldn't take the chance as smaller vessels don't always have and you can't rely on radar either.

I do think you could make it work though. Similar to van living. Plan your legs based on availability. You down time will be part maintainance etc.