Vasudeva put Krishna and Balarama under Sandipan Muni's. When training was complete it was time to ask for gurudakshina, the offering to be made to the teacher. Sandipan Muni wanted to ask for something extraordinary so he consulted his wife. She asked for her drowned son's return.
When Sandipan asked for his gurudakshina, Krishna and Balarama immediately set out for the ocean. On reaching its shores, they enquired about the dead son. The sea god emerged and told them how Panchajana, a demon, had devoured the child.
On hearing this, Krishna plunged into the water and killed Panchjana. He tore open the belly of the demon but did not find the child.
Krishna then dragged Panchjana's body to Samyamani, the residence of Yama. Yama was happy to receive Krishna and returned the child. Sandipan Muni saw the true power of Krishna and blessed him.