The story below is not an Islamic teaching nor taken from the Quran or Sunnah -- it is just a simple fishy tale ...
Two fish were swimming when they saw a piece of meat dangling before them. The younger fish darted toward it with an open mouth. The older fish cried out:
"Stop! You can't see it, there is a hook inside that meat. It is connected by an invisible line to a pole outside the water. There is a man holding the pole. If you eat the meat, the hook will catch in your jaw and the man will pull you out of the water. He will cut you open with a knife, roast you on a fire and eat you. Then he will throw your remains to his cat."
The young fish stopped. The two of them swam away. But when the young fish was alone, he thought to himself:
"Let me investigate for myself how accurate these claims are."
He went back to the meat, swam around it, above and below it. He swam as far as he could in widening circles around the meat. After a long search, he said to himself:
"I've looked far and wide, and I haven't found any sign of a man, a pole, a knife, a fire or a cat. In fact, I've found no trace of anything outside this water we live in. These must just be stories."
He went back to the meat and ate it. The hook caught in his jaw, he felt himself being yanked out of the water. He saw a pole, a man and a knife, but at that point his knowledge was useless.