A long time ago in my world, a people, who lived alone in a continent-sized island away from any significant other landmass, had a schism. Half of them departed in a fleet with numerous ships into the unknown sea.

They eventually found other big islands in the horizon, some made home, but the majority continued on the endless trek. At some time, they built a gigantic ship of wood and sails (and magic surely) to float endlessly.

By gigantic proportions i am thinking some kilometers in width and lenght. Buildings built on deck, parks with growing trees, farms, and ports with a small fleet of common sized ships to embark on short expeditions.

In this world minor magic is particularly common (protection amulets, healing remedies), while flashy and fantastical feats are rare, but known of. I think some hundred magic-knowers, a dozen mages and only one true (and old) wizard per 10.000 people is a good measure. One extra thing is that magic is always connected to art (poetry, painting, dance, music, etc.)

Is it's construction plausible, considering a technology level of maybe late medieval china and surely the help of magic? Would they be able to sustain a good and healthy life only seafaring? Will societal life have any incredible problems?

  • $\begingroup$ It's hard to answer this without knowing a few things. Firstly, do you ever intend for it to be anchored for long periods of time, or do you want it to float freely with the wind and currents? If it is the latter case, is your magic capable of steering it to keep it from running aground on islands? Because something like that would normally be incredibly difficult to steer. $\endgroup$
    – Redbud201
    Jun 24, 2021 at 21:20
  • $\begingroup$ Surely this is up to you? Can your 1 in 10,000 wizards do this? If they can cast a spell to build a massive boat, make food, then sure, they can do this. $\endgroup$
    – Nepene Nep
    Jun 24, 2021 at 21:51
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    $\begingroup$ A "continent-sized island" is a continent. If you're asking "without the use of magic, could any civilization in the real world circa 1500 a.d. have built a ship spanning kilometers?" The answer is no, because none did and we still cannot today. If you ask, "knowing they would have the help of magic, could any civilization circa 1500 a.d. have built a ship spanning kilometers?" The answer is yes, because you can do or justify anything with magic. $\endgroup$ Jun 24, 2021 at 22:43
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    $\begingroup$ Please remember that we're here to help you develop and consistently use the rules and systems of your fictional world. A better question might be, "I am developing the magic system for my world. What problems would a 2 km diameter ocean-going vessel built using circa 1500 a.d. Chinese technology experience that I would need to overcome with magic?" A question like this focuses on specific issues that would guide the development of your magic system and help you understand the limits of your world's technology. $\endgroup$ Jun 24, 2021 at 22:47
  • $\begingroup$ What is the population of you ship-island? $\endgroup$
    – NomadMaker
    Jun 25, 2021 at 5:47

3 Answers 3


Some questions you need to consider:

What can your magic do for the ship and its builders?

Does your magic make the ship stronger or more resistant to storm damage or easier to build?

How big are the trees on your islands? How strong is the lumber? How plentiful / fast growing are these trees?

Bigger ships mean more lumber which means more/bigger forests. And that lumber must be stronger, unless magic is reinforcing the design (see 1st question). A 2 square kilometer ship would require tens of thousands of planks, which would be thousands of trees. How much forest do your builders have access to?

Some assembly required

The larger the ship, the larger the shipyards. Sure, the ship floats. But it can't float while it's being constructed (again unless magic somehow suspends the structure during construction). From the first beam until the hull, at least, is complete, the structure needs to be dry-docked.

Labor force?

The bigger the ship, the more people it will require for construction. Sure, your wizards can help, but unless magic is extremely powerful, it's not going to build the ship. At best, it's probably going to do things like lift heavy objects into place or provide mortars or act as power tools, not wish-level full assembly. So how many people will it require to build this ship?

How many people run the ship? You'll need full-time repair crews to manage anything that breaks, plus anyone who manages navigation, steering, and so on?

Structural integrity

How is your ship held together? How do you prevent the ship from breaking under it's own weight? More magic?


How does your ship move? Sails? How large a sail (and how strong a mast) would it take to move a multi-kilometer-sized ship? Would it just drift with the currents, then? How do you steer it? How do you not run into things and get stuck (coral reefs, islands, icebergs, wales....)


Where in the evolution of your society did everyone stop moving and devote all their resources to building this thing? How did they come up with the design plan that would conquer the various engineering challenges it faces, and then divide their labor between resource gathering, the many construction specialties, and the support roles like medical, food, and so forth? And who trained the engineers and construction specializations for this monumental task?

Maintenance and Defense

How do you get to parts of the massive vessel that need repairs while it's under way? How do you replace broken timbers -- or even become aware of them -- when it's so large? If a fire broke out, how would it be contained? How does the ship defend itself from outsiders (pirates, invaders, etc.)?

A possible alternative:

Rather than hand-wave all of the above problems with "Magic! [insert glitter here]" have you thought about using a flotilla instead?

If, rather than one giant ship, you have hundreds of smaller ships, all lashed together, then you solve most of the problems I raise above.

  • The entire flotilla could have grown organically over time as new ships were built or acquired, and then added to the flotilla. No need for a genius master plan up front!
  • The resources to build the flotilla wouldn't have to be gathered all at once, but could be gathered over years or even generations.
  • If a storm is on the horizon, the flotilla can separate into mini-flotillas or into individual ships, making survival of the whole far easier and safer -- the loss of any ship won't risk the entire structure.
  • It's far easier to navigate a smaller ship than a larger one. If the flotilla needs to steer around an island, a shallow sea, or whatever, then they simply break apart, each sails under its own power, then reform once past the blockage.
  • It's much easier to build a small boat that floats than to build a massive floating city or mini-continent. Fewer resources, easier engineering, safer for workers. Faster, too.
  • Defense from attack or fire is easier: unlash the ships and spread out. If the pirates attack a ship, then other ships break free of the flotilla and surround the pirates. Suddenly the pirate ship becomes part of the flotilla and the pirates... well.. that's their problem.
  • Fire? immediately unlash from the burning ship and spread out until the flames are under control or the burning ship sinks. Safety first!
  • Magic isn't as necessary to make it work. But it still helps! Your mages can be useful for gathering sufficient food, for reinforcing the links, for gathering materials, for navigation, etc. etc.
  • Each ship is a family home. Each has it's own character -- custom paint jobs, decorations, designs... Each ship tells a story, just like homes do. Entire regions of your flotilla may have similar designs as they were formed at roughly the same time, but travel a few dozen ships away and the designs might be completely unique. Personally, I think that makes a more interesting storytelling framework than 1 giant ship. Picturing this big conglomerate of mismatched ships, all tied together into one giant community? I can see that in my mind, the whole undulating with the waves. But 1 super-ship? That's much harder to picture as a thing that could exist. (Pure opinion, here)
  • Not as susceptible to storm damage. One big thing can break under the strain of rough seas like during a hurricane. But a a flotilla of smaller ships can ride out storms, for the most part. Sure, a bad hurricane might cause some losses, but not catastrophic losses to the entire flotilla.
  • History. In general, human-occupied locations grow over time. There's history as people expand a city and as technology changes. Very rarely does an entire kilometer-wide area just spring forth, fully planned in advance. The flotilla concept easily accommodates the way historical cities grew from small towns into the chaotic maze of streets and buildings and parks that the residents know and love.
  • Food gathering is more readily handled, since the outermost layer of ships can all be fishing vessels that break away during the day to set out nets, then come back. The flotilla becomes their harbor, so to speak, rather than trying to feed the entire civilization from the deck of a single ship.
  • Harbors can be used without special treatment. A massive ship simply can never approach land. But smaller ships can break free of the flotilla, come to harbors/ports to trade or collect supplies and then return without any special effort. The flotilla stays at sea, but traders can move freely between flotilla and shore as needed.
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    $\begingroup$ Your answer was pretty much what I was looking for. The list of problems will help me develop both the magic and the ship (or maybe the flotilla). I will accept it as the answer, thanks! $\endgroup$ Jun 28, 2021 at 11:32

The ship is nearly uninhabited.

A colony ship designed for thousands now hosts a population of a few dozen. Large areas of the ship are unvisited by the main characters and what goes on there is unknown. Magic tenders (I am thinking of the robots in Castle in the Sky) keep the ship floating and moving. There is easily enough food for all inhabitants growing in the farms and gardens.

The ship at one time had weapons, smaller ships and many other features. Nearly all of this is unused by the current residents. The younger ones who were born on the ship know little about these other aspects of the ship, which can be discovered in the course of the story.

Storywise this lets you sidestep big societal issues and instead concentrate on the adventure of a few characters. The fact that the boat is an ancient think and current users are more or less ignorant of its construction and maintenance lets you finesse all that as well. The boat is a fine place for an adventure and you can have adventures with the things they encounter, with the meta-story being your young characters wondering about their place in the world and if the boat is their only possible destiny.

  • $\begingroup$ Your answer opened a door to a possibility I hadn't thought of. Thank you! $\endgroup$ Jun 25, 2021 at 11:10

Use Live Wood

The thing about wooden ships is that once they get too big, large waves cause them to resonate and shatter. In general, wooden ships more than about 30m long can't survive rough seas. While some ships like the Chinese Treasure Junks or the Greek Tessarakonteres were much bigger than this, they could only safely leave port during calm weather, and had to be dry-docked to survive major storms... but that is because of how dead dry wood behaves. Live wood however can be very pliable.

Since you have magic, consider having your wizards magically grow a living massive colony of intertwined floating plants. So in your case, the the "ship" is in fact "made of wood" but because it is green wood, it will not shatter from resonating with rough seas. This also makes it self healing, much more resistant to burning, and easy to have start off small and grow over time which should address many of the concerns CaM brought up in his answer.

It could be that the original ship was the result of a spell just meant to make a living normal sized ship, but because it was alive, it continued to grow and spread out until reaching its present size.

  • $\begingroup$ This is awsome! The ship being a living organism is a great alternative. I will be using this surely, thanks. $\endgroup$ Jun 28, 2021 at 11:29

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