A long time ago, on the shores of a mighty sea, on top of a cliff, lived three sisters. The elder two sisters were barbaric, living on human flesh. Every night as ships came along the coast, they would go and stand along the shore and sing sweetly. Their haunting melodies would lull the already tired seamen into sleep. The ship, without anyone to steer it, would crash into the rocks at the bottom of the cliff. They would wait until daylight and then feast upon the bodies of the sailors washed ashore. 

"Poor seamen! Please stop it! God will be angry with us. He will punish us," the youngest sister would plead, but her entreaties fell on deaf ears. Day after day the wicked sisters carried on their barbaric practice, murdering poor seafarers. Finally, the youngest sister could bear it no longer. Every night when her sisters went to the shore, she would slip out of the house and go to a point on the shore a little off where her sisters were, out of their sight.  Just as she heard the eerie strains of her sisters, she would slip into the water and swim out to the sea. When the ship would impact on the rocks, she would with the help of her enchantment carry the sailors who were alive to a far off safe place where her sisters couldn't get at them. The evil sisters in the morning were perplexed by the decrease in their game, but did not in any way suspect their little sister to be at the bottom of the mystery. This practice continued for days, with the youngest girl carting away the living sailors to a sheltered haven. 

Until finally God could bear it any longer. One rainy night, as the sisters sat huddled up in their tiny cottage waiting for the next ship, they heard the crash of thunder. The water in the sea began to rise slowly. It came some distance up the coast, some more, and still some more until it reached the hut. The sisters ran out screaming in terror. There was only water all around them, no place to go. Panic gripped their evil  hearts. "Oh God! Have Mercy," they cried, begging for forgiveness. But no, it was too late. The eldest sister was snatched by the raging waters first and she was dragged, screaming, into the murky depths. The middle sister was next. When the youngest sister felt herself being pulled by the current, she tried to cry out to God but all she could utter was 'Eeeeee.' She saw her legs and hands changing to a tail and fins. Her skin became gray, her hair fell off.
 
And lo and behold! She was changed into a dolphin! God had given her the opportunity to continue doing her service to the seamen, saving them during distress. As for her elder sisters, some say they were dragged down into Poseidon's kingdom to work as his slaves, while others say God took pity on them and changed them also into dolphins, giving them a chance to redeem themselves. 

From Ashwin Ananthakrishnan