The world was created by Bach, that is the only thing anyone knows. She worked her Bach magic and suddenly there it was, albeit covered in water but everyone in that time knew that Winter was coming, and it wasn't going to be pleasant.
So a long time ago, before the earth and the sea became separate entities due to the first global ice age, there was a fish. This fish was named Hydrocarbon and was considered by many of the Campowikia family as the founder of their majestic race. Calm and wise, he was not. But innovative and arrogant he was and slowly he grew legs and then arms. He lost his fins and scaly texture and then his gills until he looked like a perfectly normal human, except he had a tail and no matter how hard Hydrocarbon tried he couldn't get rid of his slightly more than ugly tail so he swam to the depths of the sea where he met a beautiful woman, just like him, named Royal. Soon the two fell in love and got married, well their type of marriage was much different than many of ours, and the soon had a pair of twins named Wind and Raid.
The two twins didn't have tails though so couldn't swim. Royal, fearing her boy's safety decided to take them to the surface lands which were beginning to freeze over due to the first ice age which was approaching. She laid the twins on an iceberg and left them, returning to her husband Hydrocarbon, who by then wanted more children. So Royal gave in and hoped this child would have a tail, just like them, however she was wrong and she gave birth to Nicki, who was beautiful in a quiet sort of way and so she had to swim up the the surface and lay Nicki on the same iceberg she laid the twins on.
They tried again, this time Royal gave birth to Waves, but alas she also had no tail but was twice as beautiful as her sister Nicki but not as smart and finally giving up on having more children she swam to the surface, left Waves on the iceberg and descended down into the deeps, but not to Hydrocarbon.