I found a few interesting facts about it:
- Seaking and Goldeen are the only Pokémon that can learn Waterfall through leveling up, making it possible to finish any game without the HM.
- Seaking's number in the Sinnoh Pokédex and the Johto Pokédex are the same: 079.
- Despite its name being Sea-king, it still has a 50% chance of being female.
Apart from that, its just that it looks like a dumb fish. To answer the part about the swearing and all, its just people who are not all right making some stupid Meme's and posting them on Google Images. It looks like a fish which is floppy (Magikarp, Feebas) and is therefore made fun of.
Some of them are also forced. They are made to force into the internet culture. Some of them but not all are like that.