How would sea travel develop if certain parts of our oceans were filled with monsters?

The setting

It takes place on our lovely Earth. No geography changed at all, and you'll see why I wanted to clarify this.

The monsters

The smallest monsters are 200 meters in length and can travel at 75 knots, while the largest are 800 meters in length but can only travel at 30 knots. Still quite fast though. For all intents and purposes, the monsters could only possibly be killed by a nuke. But of course, Cristopher Columbus wouldn't be able to get his hands on one.

As I mentioned earlier, only some parts of our seas and oceans would be infested with these nightmareish creatures. For whatever reasons ( insert handwavium here ), the sea monsters need to eat lava, so they never stray further than 100 kilometers from any volanic centre ( and they can go from the surface to the bottom of the ocean and vice versa with ease ). Right now, at the top of my head comes the "Ring of Fire" around the Pacific.

They ( the monsters ) are hyper aggresive, attacking any and all humans dumb enough to travel by water in their 100 km radius.

And for anyone whom might ask ( I don't know what you might need to know this for ), the monsters can travel from a radius to another if they overlap.

The question

How would this affect the development of sea travel?

Edit : As pointed out by user535733, submarine volcanoes can go dormant. Since the sea monsters already have handwavium, let's give them some more and say that they can somehow make those volcanoes active again. Because magic.

Edit 2 : Alright, way too broad. Time to change this question up a bit.

Edit 3 : The monsters will always attack a human within their radius. Going in their territory is asking to be gobbled up by them.


closed as too broad by StephenG, bilbo_pingouin, elemtilas, Nahshon paz, JBH Dec 9 '18 at 15:09

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

  • $\begingroup$ Relevant: en.wikipedia.org/wiki/List_of_submarine_volcanoes. Includes a map. $\endgroup$ – user535733 Dec 8 '18 at 20:15
  • $\begingroup$ Some submarine volcanoes have not erupted for hundreds of years. How long must the seamount be dormant/inactive to become uninhabitable to monsters? Conversely, how quickly will a new-active volcano without neighbors be colonized by monsters? $\endgroup$ – user535733 Dec 8 '18 at 20:17
  • $\begingroup$ I appreciate your efforts to reduce the scope of your question, but I think the "development of sea travel" is still quite broad. Also, one critical point missing: how many of these monsters are around? Do we expect them to get any boat within their range, or you'd still have a substantial chance to get through without meeting them? $\endgroup$ – bilbo_pingouin Dec 8 '18 at 21:35
  • $\begingroup$ Related: worldbuilding.stackexchange.com/questions/99916/… $\endgroup$ – Dubukay Dec 9 '18 at 3:33
  • $\begingroup$ Mine is the final VTC to close. It may seem irrelevant as an answer has been selected, but I'd like to point out that a vague and broad question has lead to a vague and broad answer. Perhaps the OP was benefited by this experience, but no one else will be. It's too bad, because this could have been a poignant question had more specifics been provided (tech level, ubiquity of monsters, and a focus on a specific problem rather than all sea travel through all time). $\endgroup$ – JBH Dec 9 '18 at 15:14

Ocean hazards are part of ocean travel.

Sailors know about geographically bounded hazards to shipping. Coral reefs are a good example and there have long been efforts to mark the location of reefs and otherwise ward ships away. Cape Horn is another example of a very hazardous area for ships, with a number of routes around it trying to minimize danger from currents, big waves, wind and ice. The monster Charybdis in the Odyssey is thought to have been a large whirlpool in the straits of Messina, and another geographically bounded shipping hazard.

These monsters are just another sort of natural hazard, like a whirlpool or a coral reef or an iceberg. Oceangoing commerce would have the areas known to contain monsters mapped out. Sailors would give these areas a wide berth, just as they would a reef. Just as some ships still hit reefs, the monsters would still sometimes catch a ship.


Travel and Transportation

This makes sea travel prior to the invention of precise navigation (chronometers and sextants) risky. Even if there were maps with this 100 km radius, the navigator might mis-estimate the position and get the ship destroyed. And even if there is precise navigation, prior to the invention of reliable steam engines a ship might be driven off course by a storm. That would be less frequent than stumbling onto a sea monster without maps because the captains would know here there be dragons and do their best to avoid them -- running their ships against a shore if need be.

So scratch any open-ocean travel. There might or might not be coastal and river craft.

A chicken-and-egg-problem. No big ships without chronometers, no chronometers without big ships.


This will have significant effects on economic and industrial development. Water transport is much cheaper than oxcarts or stage coaches, and now it will be missing. People traded tin from England to the Mediterranean in ancient times. Would that have happened if people had to hand-carry it across the Europe, like they did with amber?

Man's Place in the Universe

Wolves are kind of scary. So are lions and bears and hippopotamuses. But in the end organized, communicating humans can deal with them and drive them out of "civilized" lands.

Whales are a bit more tricky, but they can be hunted as well.

But there is something in the world they cannot defeat. Will they believe that a God made them in His image, and told them to subdue the Earth and have dominion over the fishies, or will they see the world as a much darker, more dangerous place?


Such large beasts would surely not wander around the coast in shallow water and complex coast line. We all see what happens to whales when they get too close to the shore, and whales are small when compared to these monsters.

This means that most of the ship trade done in the antiquity would be safe: they used to travel close to coast because they had no instruments to determine their position.

Then it is also reasonable that mankind would develop countermeasures to mitigate the impact of these monsters. We have managed to "mitigate" wolves, tigers, lions, deserts, jungles, there is no reason to not add another item to the list.


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