Once upon a time, there was a man who was living in north Sumatra. He lived in a simple hut in a farming field. The did some gardening and fishing for his daily life.
One day, while the man was do fishing, he caught a big golden fish in his trap. It was the biggest catch which he ever had in his life. Surprisingly, this fish turned into a beautiful princess. He felt in love with her and proposed her to be his wife. She said; "Yes, but you have to promise not to tell anyone about the secret that I was once a fish, otherwise there will be a huge disaster". The man made the deal and they got married, lived happily and had a daughter.
Few years later, this daughter would help bringing lunch to her father out in the fields. One day, his daughter was so hungry and she ate his father’s lunch. Unfortunately, he found out and got furious, and shouted; “You damned daughter of a fish”. The daughter ran home and asked her mother. The mother started crying, felt sad that her husband had broke his promise.
Then she told her daughter to run up the hills because a huge disaster was about to come. When her daughter left, she prayed. Soon there was a big earthquake followed by non-stop pouring rain. The whole area got flooded and became Toba Lake. She turned into a fish again and the man became the island of Samosir.