I’m thinking that there will be one small continent, about half the size of Australia or a bit larger. The single, massive ocean is inhabited by an aquatic humanoid species (yes, think mer-people) that speak to one another in a way that is similar to the sounds that whales make. They do not communicate with the alien species that have settled on the planet’s lone continent via space travel.
The ‘land-loving’ aliens have learned that the mer-people (I haven’t come up with a name for them yet) don’t mind them fishing from shore or heavily fortified boats (I might end up changing this to hover crafts of some sort), but that they become hostile when the aliens attempt to swim in the ocean (this isn’t the only reason that the aliens avoid swimming: there are several species of carnivorous, gluttonous leviathans that inhabit the ocean). The mer-people live in harmony with the leviathans, but the alien species are attacked by them on sight (still thinking on why the leviathans leave the mer-people alone).
My question is: Where did this continent come from or how did it form on a planet that’s almost entirely encompassed by one massive ocean and how large a human or humanoid species population could inhabit such a small amount of land?
Also, if anyone sees anything unrealistic in anything that I’ve mentioned, please let me know.