Undersea Kingdom Categorization.

1. Formerly a land kingdom but just look what happened.
2. Currently operates like land because of magic, divine providence, supertechnology, etc.
3. Sea creatures.

Those are the categories I can think of. Do they cover everything? Watery aliens are three, ghosts and undead are one, the future is two. Atlantis one, Jabberjaw two, Snorks three. Yeah, I think that just about does it, but I'm open to correction.

Addender

The aliens will live in different regions of the same planets. Thus will coexistence flourish, and when plagues break out, each species will bring in doctors and nurses from an immune species.

Addendum

The same won't be true of the other planets we will undoubtedly colonize because far smaller regions will be inhabited. When you can pick and choose the best places, you don't want to leave anyway.

Earth's Future

Canals everywhere. Every continent divided into even grids by canals. Cars: Obsolete. Trains: Obsolete. Planes: Rigged for water landings. Bicycles: Retained for health reasons only. Motorcycles: I'm pretty sure they're used to annoy everybody even today, so nothing will change there.

Addendum

And if they have a thousand distinct terms like terrestrial conveyances do, all the better. Quick, which one's a brougham? That's an easier one, as you can tell because I remembered the name.

Fantasy Spaceships

Often they're based on sailing ships, but likening space to the oceans is a more recent thing. Fantasy spaceships should be reminiscent of chariots, wagons, and carriages.

Addendum

That old sailor is a sea god, but you won't find that out for a few books, or maybe in an interview.

Shark Counterattack

It was a hard battle which did much to blood and bone, but the villagers subdued the great shark and killed it. They then looked upon it and wondered, full of anger and bafflement, what use they could make of it.
Till Ollepor had his inspiration. "We can bear no more of this, and this is our opportunity to stop it." He hollowed out the shark. He took out its guts, and he firmed up the insides with beams, and he made the tail a rudder too. He made the fins into oars and did everything else necessary.
Then he bade the villagers, the brave ones, the strong, to gird themselves and enter the shark with him. Together they sailed forth and down, far below to the seat of the sea king where they offered battle. Spear went against spear and net against net, and in the end the veterans who had defeated the sea's heroes before did so again.
"I am defeated," the sea king confessed. "And what now?"
"Now, rain," Ollepor demanded, and so it was done. The clouds took away great gallons of water so that the village soon sat on a cape. The sea king sent the villagers back and along with them another shark filled with gifts, and ever since the war shark and the treasure shark were the symbols of the village, later a town and then a great city.
Finis

Visible Progress

"These things that aren't fish."
"Yeah?" Neither man halted for the conversation. They had hauling to do.
"How come some of them have eight leg-thingies and others have more?"
"You don't know?"
"Would I have asked if I had? Your voice isn't that lovely. There, you've had enough time to make up an answer."
He shook his head. "No, everybody knows this one. We're just finding out you aren't an everybody. Sort of an outsider, if you will. They've got more legs because they leveled up more."
"That makes sense." The man looked closer at the squids and octopodes caught in the nets. "Yeah, it's not impossible, but . . . Whoa!"
Strong as they were and used to the work, the next load demanded from them almost more than they could give. They braced and they heaved, braced and heaved, and after more time than was reasonable, they hauled up a creature of the deepest sea so thick with appendages that they could be counted only after death stilled their owner.
"Tell me if you were kidding before, because if you weren't, this guy must be . . ."
"The one who killed the Nightmare Emperor!"
The fishermen bowed to the slimy hero and released him.
Finis

Addendum

I won't insult your intelligence by reminding you to set a number of continues.

Important Worldbuilding Question

Before you start your first draft, ask yourself: Do people in this setting get hurt if they touch spikes on the side? How about water? Does it kill them instantly? Suppose someone runs into an enemy. Is that enough for damage, or is an attack required?

The Qualifications of Officials

Local knowledge of the Eternal Whirlpool should not have been necessary for anyone to stay away. And yet, one day townsfolk on the north shore and townsfolk on the south, two different towns, saw a boat rowing far too close to it.
"Hey! It's dangerous! Hey!" The southerners called out, grabbed ropes, and sailed as close as they dared. "Jump out! Swim over here! We'll haul you in!" But the northerners simply watched.
The lone man in the boat went against the warnings, ignored the stars, and thought nothing of the whirling waters. He rowed straight forward till the force of the Eternal Whirlpool made it impossible to do anything without curving. Down he spun, and then he was gone.
The southerners cried and wondered what had led up to the loss of life while the northerners looked as if they knew, as if the same idea had occurred to them. Either way, there was nothing to be done.
Three weeks later, eternity abandoned the whirlpool. It straightened out and became as predictable as any watery way governed by currents and tides. Strangeness remained above it, for a man stood there as if on land, the Spiral Crown on his head. He called the townsfolk and all heard him regardless of distance.
"I have recovered the Spiral Crown and restored with it the epoch of hero-kings. This will be my capital, both towns together. Those in the south, who attempted to aid me, will become the rulers of counties, and may your benevolence be an aid to the world. Those in the north, who trusted me, will become the judges, the treasurers, and the generals, and may your stolidity be a bulwark against the world." And all was done as he said.
Finis

An Alternate Earth

What if the land were sea and the sea land? Not enough water, for one thing. The Panama Bridge would still be pretty good.

The Difficulties Are Perhaps Insuperable

A pebble bounced down the hillside and straight off the island. Doanu watched its progress while Ferdin stared at the ships entering and leaving port. "You know, Doanu."
"Doubt it." He kicked another pebble.
"I bet we could apply some of the construction principles of our ships to build ships suitable for other environments. Obviously we'd have to make all kinds of adjustments, but I really think it could be done."
"'Other environments?' Come on. What are you talking about? I shouldn't ask. I know you have no idea either."
"I'm talking about seaships, lakeships, riverships. All kinds of ships. Waterships!"
"Uh huh. Why would we want those?" Doanu swept his hand as if to mark all the sky surrounding the island with gold paint. "What are we missing here?"
"You never know."
"Hey! I'm not going up there after you clowns!" They looked to the foot of the hill and saw Ranoal waving for their attention. "Chief Lanneoru wants us! The order came down! We gotta reduce the oil usage!"
"Geh. Stupid oil." Doanu began to tromp down the slope. "What a pain. Where do you think those 'whale' things come from, anyway?" "I don't know. Maybe we can find them someday. With waterships!"
Doanu snorted.
Finis

The Reddened Firmament

The claim is made that four moons once ruled the sky, alike in their luminescence and their envy. The four armed themselves against one another and fought so that men and animals of ground and sea saw nothing above but mayhem, and birds descended out of fear. Some, they say, have never regained their courage and still walk or swim. The moons died in fraternal strife but one, which rules today as the sun. As for the others, the blood of the first comes as rain, of the second as snow, and as to the third, a lake high in the mountains collected all of it. Fratricides who bathe in it will be relieved from their pollution.
That is the claim. Believing that, a man walked alone and climbed those heights, for he was guilty of that crime. The lake was there from which no river carried the cloudy liquid, and in it the man bathed himself that night.
There his eyesight became as clouded as the water. The world around him dimmed, and he heard a voice say this. "Was it wrong, what you did?"
"No," he whispered.
"Was it wrong?"
"No," he said.
"Was it wrong?"
"No," he shouted, and his throat burned.
"Take this weapon, and with it wreak what is no more a crime than what you wrought before."
He stood and left the lake, and in his hand then was a javelin famous enough that he had heard of it as had every man, despite that it came to be that very day for the first time. It was the sun-slaying spear, and there was justice and piety in the world before he used it.
Finis

The Munificence of the Heavens Is Without Limit

"When the orange moon fills Syevor Pond, you will fill the position you desire." That was the claim. Mr. A, as we shall call him, did not believe in superstition, but he believed very much in filling positions. As a consequence, he informed his secretary and his associates he had decided to take a few days off ("So soon before the chancellorship is decided? He must be confident."), planned his trip, and traveled to the town nearest Syevor Pond, which of course was called Nyaddavar.
Mr. A had his doubts when he crept through the concealing night toward the pond. Where was everybody? Was that not a widespread belief he had heard? The orange moon was full, and as for the brown and green moons, they were probably lucky too. But he was all alone as he divested himself of anything better off dry and walked into the pond.
He waded into the center of the pond, the blue waters turned orange by the looming moon, where he became embarrassed. Who else was there but Mr. B and Mr. C, his rivals for the desired position? The three pretended not to recognize one another while elbowing and shoving for that coveted spot in the center of the moon as it was reflected.
"Ahem," Mr. A said. "Gentlemen, this silliness is beneath us. Above our toes possibly, but otherwise beneath us. This superstition is nothing but, well, superstition. The same future cannot come true for everyone at once. Imagine if there were twenty of us in this pond. Or twenty-one! Hmph." Mr. B and Mr. C agreed, though their elbows had reservations. In any case, the night passed amicably enough despite the obstacles to it, and all three returned from their vacations rested, ready, and biting their nails.
Mr. A got the job. Hurray! So much for orange moons and ponds, he thought until he heard Mr. B had an offer from Nmeleurda, which was looking for a chancellor, and Mr. C from Mden Fdan, which suffered from an urgent need for the same. All three became chancellors just as the superstition said, and all three broke out in hives for five days for doubting it. Because every superstition is always true, even if it that is impossible.
Finis

Addendum

The origin of the feud was an argument whether to put the tea or the water in first.