Hollow Sea World?


Homebrew and House Rules

RPG Superstar 2012 Top 32

Has anyone else done this:

A world similar to the Hollow Earth (with all the activity occurring along the interior of the sphere, so you can see the opposite landmass overhead; gravity is directed away from the center of the sphere and towards the interior surface of the sphere), but instead of it being an earthy sphere, it's a watery sphere.

So the "sky" is actually the same body of water you're swimming in, just on the opposite side of the sphere?

I just thought of this. I plan on running a "flying continent" campaign, and originally it was just going to be spinning above a regular flat ocean, but then I thought of this.

But how would the sun work? In most Hollow Earth-type worlds, there is a sun or other light source in the very center. I don't want that. I want a regular sun and a regular moon.

Could the sun and moon just float through the waters of the "sky?"

The campaign is going to have lots of airships and flying mounts and carpets, etc., already. Should the sun and moon be places you can journey to?

Or should I reserve this idea for a different campaign? One where floating armadas, cities, and (volcanic) archipelagos light up the (eternal?) night like stars?


I've never done anything like this, but if you go with a more literal definition of Genesis this actually might be the case for Earth and you can read more about it here.

But I'm fairly certain that's not what you mean, so I'm sort of assuming what you are trying to describe is something like a giant sphere of water, the outer edge of which meets space (or whatever) and the inner edge of which is where your setting takes place.

There's actually no reason a sun and moon (or multiple suns and moons) couldn't pass through the water or even just float outside it. It really depends on whether you want day and night (if you do there has to be some way for the sun to set) and how you see the topology of it. For instance, if a character that can breathe water infinitely started to swim away from the hollow center where the civilization is, what would that character encounter?


Another problem is physics. Just how much real world physics are you gonna use? The sun passing through the water would cause the planet to flash into steam. Has sun been getting ever closer as the planet orbits, slowly evaporating? Do the inhabitants know their world is shrinking? Are there doomsday cults waiting for the planet to dry up?

Then the moon. Does it carry a bit of the planet away every time it passes through, or does water roll off the moon like a duck's back? Maybe as the planet evaporates the moon melts, dripping more water into the hollow ocean?

The idea does sound like a unique take on the idea of a hollow earth though.


If the sun rises and sets, then there would be a point in the sphere where you can go to reach the sun every day. What would that place be like? Is it a desolate region with little life because the sun passes through the area killing everything? Is it an island with a great volcano that spews forth a ball of fire that lights up the sky? And what about where it sets? Does it burn out and fall harmlessly to the ground/sea, or is there some scorched wasteland that has been burned by a million sunsets?

As for the moon, it could some object passing through the sphere, or it could be an orbitting object which passes overhead, obscured sometimes by the glare of the sun, and perhaps possessing a bright and dark side. If it comes out of the water, could you ride it? Could there be subterranean areas where people live in airtight structures? Do killer whales get stuck on it, or is it actually their home?

And since the sphere is water instead of earth, the question of what is beneath you is even more relevant. What happens if something keeps going deeper and deeper? Does it reach space? Does it come out the other side like pac-man and asteroids?

Lots of fun possibilities really.

The other side worth considering is the way it changes society. If you can see other places, you can spy with a telescope. You can map out large portions of the world just by looking up, as can your neighbors, making exploration a very simple prospect. And signalling others from extreme distance is easy, all you need is light. Long range communication is going to develop more easily than short range communication.


You could have the sun orbit outside your hollow sea. So that the 'day' is when light streams from the ocean, and the 'night' is when light is coming from the distant sky. The ocean would get unbearably brighter as you go deeper, until the bottom of the sea becomes pure steam and fire elementals.

RPG Superstar 2012 Top 32

I'm kind of like the giant volcano belching out the sun every morning. Either that, or a sunfish. :-P

Maybe a moon made of ice?

Obviously, physics is going to have to be tweaked.

For my vanilla flying continent campaign, I have a fictional physical force called "aversity" that pushes objects apart. But it's even weaker than gravity, so its only noticeable with very massive objects, like planets and flying continents. It not only keeps the continents from falling into the ocean, but it generally keeps them from crashing into each other. It also keeps the continents aligned along their north-south axes.

Scarab Sages

Are you perhaps thinking of Titan? :)

Community / Forums / Pathfinder / Pathfinder First Edition / Homebrew and House Rules / Hollow Sea World? All Messageboards

Want to post a reply? Sign in.
Recent threads in Homebrew and House Rules