Is my plotline possible? If so where should I set it?

Hey guys, been lurking and posting here for a while now, love some of the content on here. I’m currently trying to write a story and I am struggling to define some of the parameters. <br><br>**Plotline:**<br><br>The story I am trying to write is set in a world where there has been an (unspecified) apocalyptic event, that has left only one or two major cities remaining (or it may just be that my characters don’t know if there are others, I haven’t decided). The story itself is (hopefully) going to be about the characters getting from one city to the other, with the entire journey being by sea.<br><br>My main character is a historian, and his specialism is navigation (it’s a long story, just roll with it). And he believes that if they follow a historical route (either the (Ancient) Egyptian spice route, the Norse passage to Iceland, or the Polynesian route to Easter Island) they will get to the other city, therefore he and his (small) group of followers try.<br><br>**So here is the question:**<br><br>Is this plotline possible? If the plotline is possible where is the best places to set it?<br><br>Some things I have already thought about:<br><br>* The world would (most likely) have to be completely devoid of metal, as this would make things too easy<br>* The characters are from a city, so they will have limited (if any) sailing experience. I don’t know enough about sailing to know if a group of people who have never sailed before can (successfully) navigate an entire sea (with nothing but historical records of the route). I’m guessing that it would be incredibly hard, but I don’t know enough to make the journey realistic. <br>* As they are from a city, they will also have no knowledge of gathering food and water in the wild, so there may need to be islands with fresh water and food along the way.<br><br>Some things I (obviously) haven’t thought of that you guys might see right away:<br><br>* Climate disaster. If the sea journey is possible, is there a (realistic) apocalyptic event that would completely remove all landmasses of human habitation, yet still leave the sea roughly as it is now. I know (for example) that global warming will inevitably raise sea levels, but that wouldn’t completely remove all landmasses. I can (of course) say it’s magic, but I would rather not. <br>* I just assumed that a historical sea route would be easier than just “going East (for example) and hoping to find land”. With no magnetic materials to make a compass, would this still be true?<br><br>If anyone has any thoughts on this, it would be greatly appreciated. I know that I suck at geography, so if you can see an obvious flaw in my plans, please let me know.<br><br>Thanks in advance (and apologies for the long post)<br><br>TL;DR: Is my plotline possible? If so where should I set it?