I am working on a setting whose low-tech inhabitants are starting to launch long-distance voyages of exploration (preferentially by sea, because travel that way is so much faster than on land). They have outrigger canoes with paddles, and are working on sails.

The limit to how far a team of explorers can go, would seem to be primarily set by supplies of food and fresh water. Along the coast, they can stop to collect water from streams and rivers. For cross-ocean voyages, it's trickier. They don't really have the tech to desalinate seawater, and I get the impression a ship of size X cannot really collect enough rainwater for the crew of a ship of that size, so the water supply would have to be carried on board.

Food is a more subtle question. At first glance it seems to me that they should be able to catch fish on the way. Rationale: a fishing boat can catch more fish in a day than the crew eat, otherwise it would not be profitable! But then, I read about long-distance voyages needing to carry food, so if it was that simple, why would they need to do that?

It is said that the open oceans are deserts; the biological productivity per hectare is low because of lack of availability of mineral nutrients.

Conjecture: profitable fishing of the open ocean (aside from a handful of particularly rich locations) depends on modern technology like sonar to track schools of fish; low-tech fishing techniques like 'two people in an outrigger canoe dangle a net over the side and see what swims into it' are only profitable in the relatively rich waters of the continental shelves.

That would suggest that low-tech explorers can indeed feed themselves along the way by fishing if they are sticking to the coast (where they can also land from time to time to gather berries or suchlike for vitamin C), but when they want to set out across the ocean to find other continents, this will stop working, and they will need to carry food for the voyage.

Is this correct, or am I missing something?

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    $\begingroup$ i don't know, but i'd imagine that fishers go where the fish are, while explorers will potentially want to go somewhere else. $\endgroup$
    – ths
    Commented Jun 23, 2021 at 13:14
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    $\begingroup$ "Is there some factor that drives fish to congregate in more specific locations?" Start with the Wikipedia article on the Great Banks and continue from there. There must have been a reason for European fishermen to prefer to cross the ocean instead of fishing somewhere closer to home... $\endgroup$
    – AlexP
    Commented Jun 23, 2021 at 13:46
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    $\begingroup$ @AlexP The big advantage of the Great Banks and similar places is the water is shallow enough to drag your net on the bottom, allowing both catch of bottom fish (cod, flounder, etc.) and avoiding other fish swimming out of the bottom of your closing net. Same level of effort produces more fish and better price per weight. $\endgroup$
    – Zeiss Ikon
    Commented Jun 23, 2021 at 13:55
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    $\begingroup$ A rowed outrigger could reach speeds of up to 9 knots, possibly more with sails. Vikings averaged this speed during their years of rape and pillage in boats that were only slightly larger than a big outrigger canoe. $\endgroup$
    – boatcoder
    Commented Jun 24, 2021 at 17:18
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    $\begingroup$ "They don't really have the tech to desalinate seawater" - other than that, it all seems fine. What methods might an ancient civilization use to desalinate sea water? $\endgroup$
    – Mazura
    Commented Jun 26, 2021 at 2:52

6 Answers 6


Fishing is incompatible with making maximum headway, for a start -- to fish (the way fishing boats do, in pursuit of profit) you would put out nets with floats, then draw the nets closed, and lift them into the boat with whatever you've caught (see "purse seine"). This isn't something you'll do much of if you're trying to make a steady 2-3 knots of headway (which is about what ships could do on long voyages in the Age of Exploration).

Beyond that, catch all the fish you want, and your crew will still suffer from scurvy, so you have to carry land-based food -- fruits and vegetables, or at least (as the British navy did until the 19th century or later) citrus juice to provide the necessary Vitamin C in the crew's diet. Not to mention that a steady diet of nothing but fish will pretty much guarantee a mutiny before you can get anywhere far enough away you didn't already know it was there (it took weeks to cross the Atlantic in the 16th century, starting from the Azores -- and they were a week off the coast to begin with).

As for collecting rain water (say, using sails as collectors) the problem you encounter is that any surface that's been through a storm or even a good wind will be coated in salt, so the water you collect when it does start to rain will be too salty to drink; you have to pour the first barrel or two overboard before you get fresh water. Then there's the fact that rain at sea is sporadic at best, even in the latitudes where land gets daily showers.

So you're back to what the exploration fleets did in the 15th and 16th centuries: follow coasts, both for fresh water and for fresh fruit and meat, and when they must strike out across an ocean, haul along all the food and water they could (and just deal with it when it gets moldy and scummy, because it's still nutritious even if it's a little toxic).

Ship's biscuit was hard and dry for good reason: it kept better that way. Water barrels were kept sealed because without light, the water wouldn't turn green as quickly. And yes, any time it rained, they'd try to collect water -- but that was never enough for drinking needs.

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    $\begingroup$ Whale skin and blubber contains vitamin C. Inuits didn't get scurvy on their meat-only diets. $\endgroup$
    – minseong
    Commented Jun 24, 2021 at 0:08
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    $\begingroup$ The livers of most mammals are also a useful source -- though one needs to know to avoid (for instance) polar bear liver, with its acutely toxic level of Vitamin A. Taking whales as a dietary measure, however, isn't very practical for explorers -- whaling was big a couple centuries after the Age of Exploration in our history, because it required more sophisticated ships that could sail around the world routinely (whalers from New England routinely hunted the Indian Ocean and South Pacific in the 19th century). $\endgroup$
    – Zeiss Ikon
    Commented Jun 24, 2021 at 11:09
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    $\begingroup$ Just adding, as a general notice regarding long-term food, one of the reasons the Galapagos Tortoises were so over-farmed was because they can go up to a year without food or water (although I'm not certain how that affects nutritive quality) and were easy to stack upside-down in the hold so that there was a longterm source of fresh meat. $\endgroup$ Commented Jun 24, 2021 at 15:27

I don't know a specific answer, but I do know a place to start digging.

Look hard at some of the Polynesian peoples and the Maori and such. Take a hard look at places like Easter Island and who lived there. Look at the Hawaiians. These are all what some might call primitive peoples and they all carried out very long sea voyages in primitive outrigger type boats. These boats were estimated to be half again as fast as European ships.

The problems to be addressed are: Food. You can't survive on just fish. Water. You need enough to get you from here to there without it going too stagnant Navigation. They used stars and were able to accurately sail from one place to another. How exactly, I have no idea.

Rapa Nui, also known as Easter Island, is more than 1200 miles from the nearest inhabited island. The people Europeans found there were estimated to have arrived there before 1200 CE, perhaps as early as 300CE. So we know this kind of voyage was possible because it did actually happen.


The book Kon Tiki by Thor Heyerdahl may be interesting to you. It follows the real events of Heyerdahl and his team of researchers crossing open ocean in an extremely low tech balsa wood raft. The raft was propelled primarily by a major sea current, and because they were following the current Heyerdahl reports a constant presence of edible sea life during the voyage.


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    $\begingroup$ Yep, just was remembering it to make a comment. So there are other survivial stories, more than one, so as people on jachts do fish and fish more than enough(those who do) - at least transatlantic voyadjes, indian and pacific oceans. Sure they have better lines and baits and such but... $\endgroup$
    – MolbOrg
    Commented Jun 23, 2021 at 23:10
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    $\begingroup$ Kon-Tiki and also Columbus, and the Vikings who went before him. $\endgroup$ Commented Jun 23, 2021 at 23:34
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    $\begingroup$ A raft with a big sail. $\endgroup$
    – RonJohn
    Commented Jun 26, 2021 at 2:37

Alain Bombard

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This man, according to Wikipedia, "was a French biologist, physician and politician famous for sailing in a small boat across the Atlantic Ocean without provision. He theorized that a human being could very well survive the trip across the ocean without provisions and decided to test his theory himself in order to save thousands of lives of people lost at sea."

He survived a 62 day trip across the Atlantic in a inflatable raft. He subsisted on small amounts of seawater, collected rainwater, fish, and surface plankton skimmed with a net. I would not say he really fared "well," per se, but he did survive.

He had a few theories about drinking seawater. One was that the danger comes from a few angles. One is that sailors would sometimes only drink the seawater out of desperation once they were already severely dehydrated, and by that point the kidneys were far too weak to filter out toxins and salt effectively. The second was that there was an upper limit to how much salt the body could filter out in a day. You could easily drink beyond your body's capacity to filter it out of your system. So his strategy was to "drink early, but drink little." He calculated that a person ought to be able to consume about 3 cups of seawater per day, (better if dilluted with something than not, which could be collected rainwater or squeezed juices from fish). Note that 3 cups is not very much and if forced to subside on seawater alone, the sailors will be very very thirsty. But it can supplement the water supply and extend your resources.

The nutrition and vitamins were gathered with fish and skimming plankton with a net. The plankton can provide some vitamin C, and other nutrients that the fish lacks.

Now, it should be said that he had some real health problems as a result, diarrhea, sores, headaches and other discomforts. The whole situation was likely less than sanitary, but he survived.

I would definitely recommend a sail if your people can make one, to conserve energy. And a way to catch and collect rainwater whenever you can. Some kind of canopy to keep the sun off would be nice, and make sure that they stay out of the water most of the time. Soaking in seawater all the time is not good on the body.

I also don't know how many explorers you are thinking of, but what works for a small crew might not work so well for a large one. The larger the craft and crew, the more I would rely on carried supplies rather than what you can collect on the way. The very nature of exploration is wrought with unexpected turns and inconveniences, problems that start out small can grow to become much bigger problems later.

So this may not be the best all around reply, but I think other people have the bases covered when it comes to how traditional sailing vessels prepped for journeys, this is more of a survival take on the issue. I would recommend reading up on Alain Bombard. Also anything you can find out about Polynesian sailing practices. They had unique navigation methods and probably survival techniques too, but I don't know much about them. I hope this helps!

  • $\begingroup$ Interesting real-world example. +1 $\endgroup$
    – Kingsley
    Commented Jun 25, 2021 at 1:21
  • $\begingroup$ This gives me a great idea for a coastal sea-faring folk who, while not amphibious, can filter out ingested salt to the point that drinking sea water doesn't harm them. They would travel on boats scooping out barrels of drinking water straight from the sea, horrifying sailors of a different descent. A side-effect is that their taste buds are so over salted that when they "season to taste" it ends up disgustingly salty to anyone else. $\endgroup$
    – Toddleson
    Commented Jun 25, 2021 at 21:56
  • $\begingroup$ "sailing in a small boat" or "survived ... in a inflatable raft" Which is it? (Also, OP's explorers don't have sails.) $\endgroup$
    – RonJohn
    Commented Jun 26, 2021 at 2:35
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    $\begingroup$ @smci This may be the bare minimum to keep people alive, but it's not the high energy fare you'd need to supply a crew with if you wanted them to have the strength to row long distances under their power. I'd definitely pack supplies if it were a planned mission. $\endgroup$
    – Redbud201
    Commented Jun 27, 2021 at 5:06
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    $\begingroup$ @Redbud201: obviously. But I'm quibbling whether this subsistence food+water for one person is even scaleable at all, to subsistence diet for n people. Clearly there won't be much rowing. $\endgroup$
    – smci
    Commented Jun 27, 2021 at 5:28

While fishing can supplement their diet, historically they had to carry both food and water. Fishing was too undependable. Water is usually more limiting. it is bulky and heavy. Large wooden barrels were used and even then the water quality was often poor with foul taste and organisms growing in the barrels. Food had to be preserved, heavily salted meats and hardtack breads. Scurvy caused by the lack of vitamin C was an issue on longer voyages. The remedy was lime or other citrus juice although sauerkraut was also used.

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    $\begingroup$ The water is not sterile or pure when put in the barrels. There will be slime and bacterial colonies feeding on the nutrients that were in the water. Go to a local stream and fill a bottle with water form it. seal it and put it in a dark closet for a couple of weeks and then take it out and look at it. $\endgroup$
    – James Cook
    Commented Jun 23, 2021 at 13:36
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    $\begingroup$ Commercial trawlers dragging nets can usually get at least some fish, but you cannot really fish this way in a rowed or sailing vessel. It will more likely be more like sport fishing with a baited hook on a fishing line. Even in areas known to have fish this type of fishing does always catch a fish every day. Ask any sport fisherman if they always catch a fish every day. $\endgroup$
    – James Cook
    Commented Jun 23, 2021 at 13:40
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    $\begingroup$ Iron barrels for water. Iron gives a rusty taste, but keeps disgusting and dangerous things from growing. $\endgroup$
    – AlexP
    Commented Jun 23, 2021 at 13:48
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    $\begingroup$ @JamesCook Sailing trawlers (e.g. the so-called "Brixham trawlers" in the UK) were developed in the 19th century for commercial fishing, but were a lot more high-tech than the OP's scenario of outrigger canoes. $\endgroup$
    – alephzero
    Commented Jun 24, 2021 at 5:30
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    $\begingroup$ @rwallace - forgive me, but you seem to be a bit fixated with fishing boats. Fishing boats, by definition, go where fish are known to be, that is they stick to known waters; your question is about explorers, who, also by definition, explore, that is they go to unknown places. Fishermen know the fish are there and can sit still and fish; explorers don't know what they will find or what the fish situation is on the way and can also sit still, the difference being they will die if they sit still where there are no fish. Explorers are not on a fishing trip to known fishing grounds, $\endgroup$
    – Spratty
    Commented Jun 24, 2021 at 9:00

This is a "calories in / calories out" situation.

The human body adapts to the activity it does. They did research on long distance runners, and their bodies burn far less calories doing that activity than a person that doesn't do long distance running. It's because their bodies have hyper-acclimated to the exercise.

Folks working on a boat will have their bodies hyper-acclimate to the activities over years, so they will expend less calories doing them. IE: hoisting sails, etc. So, in the long run, a crew will require less calories to perform activities than, say, a fresh crew that's never sailed before.

Next, while movies have "glamorized" crews working non-stop aboard ships, that would simply be wasting calories / energy for no reason. In some situations, the captain wants to keep the crew busy to keep their mind off boredom at sea (especially, with low / no wind stalling them out). In other situations, the captain is trying to enforce discipline by making the crew do monotonous tasks, like swabbing a deck that's already clean.

But, a smart captain lets the crew rest.

Sailing is a "feast or famine" job. By that I mean there is either too much work to do, or hardly any for long stretches. The crew needs to be fresh and rested when a storm hits, or when they make land to unload / load cargo, etc. They will hit times when the wind stalls out, or they've set a course and just need to wait until the wind takes them where they need to go. The captain will let the crew hang out, play games (dice, cards, etc), play music, work on hobbies (whittling, etc), and possibly have them work on side tasks, like sewing up torn sails, mending rope, etc. The goal is to let the crew relax and enjoy themselves during the down time, because when real work shows up, it often shows up in droves.

These long periods of rest also help the crew conserve calories, because they're not doing hard labor every day on the boat. They're just doing light labor for a week while the ship does all the work (sailing them where they need to go).

So, food isn't that big of a deal. Besides fishing, crews learned to salt meats and create hard-tack biscuits and things. They would take along lard to cook food with, which is high-calorie fat (fat is 9 calories per-gram vs. 4 calories from protein & carbs).

Water would definitely be a big issue, but the crew can use the massive sails to capture morning dew and barrel it for water. Rain storms provide a lot of water. There are times when there's not much rain on the seas, but when out at sea you have a very flat view of the ocean.. you can literally see storms off to the side. You can sail into them and follow them while collecting fresh water by using the sails as funnels. Not every storm at sea is a big-wave destroyer. There are mild storms where it's just rain coming down. Crews would start to know where the rains are during which seasons on the high seas, and decide to make stops there.

What you have to remember is a planet is a closed-source environment. Water evaporates off the oceans, and has to go somewhere. That's where it gets recycled as rain that comes back down. So, if folks are sailing the high seas, they will have opportunities to get fresh water from rain.

If they are stuck out in the sun w/o rain, they can collect sea water and evaporate it into condensation and collect that en masse.

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    $\begingroup$ Just for info, the swabbing wasn't to clean the deck, it was to prevent the wood drying out and shrinking. Welcome to worldbuilding. We invite you to take our tour and read-up in the help center when you have time. Enjoy the site. (From review) $\endgroup$ Commented Jun 24, 2021 at 20:56

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