This is the legend of two fishermen who didn't fish anything for days.
A ghost appeared to them as they were on their way home and told them to fish on a particular spot on the sea. He promised they'll get rich and had to do only one thing:

Let free the most precious fish !!

The ghost was right, their net was full, they couldn't believe it.
One man took a closer look to the capture and discovered a beautiful fish with shiny eyes and fins gleaming like gold and said:"That's the one we must set free"
The other man replied:"No, we don't liberate him" and decided to hide him among the other fishes.

Soon they noticed that all the fishes on board began to turn into gold.
The boat got too weighty and finally it was sinking under the heavy load.