I'm writing a story that takes place on an island. This is an earth-like planet in gravity (though I'm willing to negotiate this one a little), climate, etc., but it's almost completely covered with shallow oceans.

What I'm curious to know is what features of the planet (since I can adapt it as needed) would make it easier or harder to maneuver a small boat? (think, something a somewhat primitive tribe could make that's designed for two people. EDIT: The two-person boats are built for speed, not range. There might be other boats for going longer distances.)

Tides can definitely be manipulated, I'm planning to have two moons and their sizes are definitely open for negotiation at the moment. If that helps, go for it. Do note, they're co-orbital in a similar style to Saturn's Janus and Epimetheus, so they have to be the same distance from the planet; just manipulate size/mass and what that distance is.

So, in short, how can I manipulate tides (i.e. moon size), weather, gravity, topography, currents, or any other feature of the planet to be maximally conducive to boating but still keeping the planet reasonably habitable by humans?

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    $\begingroup$ Just to draw a real world comparison: Polynesian cultures are spread on various islands across the width of the Pacific Ocean. They managed this with only wooden boats and sheer bloody-mindedness. ‘Reasonably habitable’ is a matter of perspective. $\endgroup$
    – Joe Bloggs
    Nov 3 '20 at 9:56
  • $\begingroup$ Very true. My main reason for putting that in is that humans will arrive on the planet later in the story, so I don't want anything like monster tides, extremely oppressive gravity, low atmosphere, huge storms, etc. I don't care at all about the islands being spread apart, almost all the action happens on one of them. $\endgroup$ Nov 3 '20 at 9:59
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    $\begingroup$ "takes place on an island" needs to change. Single island with no distant destination relegates boating to fishermen, and nothing else. Give them destinations to go to! $\endgroup$
    – user79911
    Nov 3 '20 at 10:31
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    $\begingroup$ "Almost completely covered in shallow oceans" -- and from where do they get the wood to make the boats? $\endgroup$
    – AlexP
    Nov 3 '20 at 11:19
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    $\begingroup$ @AlexP: They make their kayaks from the bones and hides of marine creatures, of course :-) $\endgroup$
    – jamesqf
    Nov 3 '20 at 16:02

Your main constraint here is the two man boat size. That severely limits the range you’re able to go. The second constraint is that you need land to break up storms. Without land you’ll end up with all sorts of nasty weather systems that will crush your island civilisation like an egg.

Other than that this is mostly a matter of co-incidence. Your moons can be tidally heated which explains the liquid water and also the high Vulcanicity of the world. High vulcanicity means lots of volcanic island chains or archipelagos that correspond to the tops of undersea mountain ranges (like Hawaii). This solves your range problem: Two men in a canoe can sail from one peak to the next with comparatively little effort. Very close islands might even be connected by tidal landbridges that are only exposed at particular orientations of moons/planet.

Now: storms. We know hurricanes can get big if not slowed by cold water or large land masses. We also know suitably large storms can turn into permanent weather systems (See Saturn of Jupiter) so it’s plausible that our storm problem solves itself: Your civilisation exists in the eye of an unfathomably large storm system fed by the endless water and tidal heating. It’s relatively calm and sunny there, with plenty of islands in the Archipelago, but god help you if you sail too far from home!

Plus imagine the mysteries to be found in the wild sea...

  • $\begingroup$ Ooh, I do like the idea of the giant storm, I might use that in another story, but I don't think it'll fit this one. I should clarify, the two-man boats are built for speed, not necessarily long ranges. These islanders aren't particularly interested in exploring the rest of the world. I'll go edit the question to make that clear. $\endgroup$ Nov 3 '20 at 10:24

You can make extremely useful tides using 2 synchronized orbits

  • A chain of islands going as far as you need, but the seas are very shallow between all the islands in the known world, 5m at high tide, 3m at low tide sorta thing.
  • 2 large moons, in a complex dual elliptical orbit pattern that looks like 2 interlocking chain links:

enter image description here

The moons have the same orbital period but are 50% phase shifted from each other. What this means is from every point on the planet, in each of the 4 major directions, there will be a moon in that direction within the next, say 24 hours, and it will be the closest moon by an order of magnitude.

How does this help? You now have Directional tides, and the direction the tide is pulling you is predictable and can be charted. On island X, at time Y, the tide will pull you exactly east. At time Z, the tide will pull you north.

With a little bit of primitive charting and map making, you seafarers can calculate reduced-or-zero-effort sea trips. No need to paddle except in emergencies or when doing fine maneuvers, just look at the chart, and wait for favourable tides.

Fit your small boats with a rudder, and you can travel slightly cross the tide too. Boating will become free and convenient. Conversely the tidal pulls combined with the shallow seas can make the seas very dangerous to swim in for novices (depending on topography you'll have rip currents everywhere), ensuring that your people discover and use boats and don't swim long distance.

  • $\begingroup$ This would work perfectly except that I need the moons to be co-orbital for other parts of the stories. In the question, I linked to the specific moons in our solar system I'm planning to model it after, you should go take a look at that. I would definitely appreciate it if you could show me another way this could work, because this is definitely a fascinating concepts. I'm curious, with co-orbital moons, would different latitudes possibly create tides that could have a similar effect? I'm not sure exactly how that would work but I thought I'd ask $\endgroup$ Nov 3 '20 at 12:23

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