Once upon a time, under the deep blue sea, small fish, and sharks lived freely together. At that time, only sharks had gills until something changed.

One day a boastful fish came to a shark and said, “Ha! Us fish have beautiful scales, and sharks have boring, gray blubber. We have closed lungs, and sharks have slits in their throats that they breathe out of. We small fish are the most gorgeous kind of creatures that live in the sea. Sharks have hideous sharp teeth that they use to kill.” The shark was very angry at the fish’s statement.

The shark retorted, “How dare you call my people ugly! We are the strongest animals in the world. If I wanted to, I could gulp a hundred of you fish at once.” “Sure you can,” said fish sarcastically.
“You will learn your lesson not to talk to sharks like that!” screamed shark furiously, and swam away.

The next day, fish was scanning the ocean floor for food. Then, he bumped into shark. “Ah, just the person I was looking for,” shark said.
“Why me?” asked fish."
“I told you I was going to teach you a lesson.”
“Wh- What are you going to do to me?” asked fish again, stuttering.
“Us sharks have a friendship with posiden. We told him that you made fun of our gills, and he decided to grant with one power. We can change any creature’s body, and we are going to give all your fish gills!” exclaimed shark, chuckling.
“No, you can’t make us ugly like you!” cried fish.
For a second, everything was quiet. There was a bright light, and then it was done. Fish had gills. That is why today, not only sharks have gills, and why other fish live in constant fear of sharks.