When Kṛṣṇa and Balarāma offered Their teacher, Sāndīpani Muni, anything he desired, he W asked for the return of his son, who had drowned in the ocean at Prabhāsa. The two Lords at once traveled there on Their chariot and ordered the ocean to return Their guru's son.
But the deity of the ocean advised Kṛṣṇa that the 'boy had been captured by a demon named Pañcajanya. Hearing this, Kṛṣṇa dove deep into the water and killed the demon on the spot. finding no trace of His teacher's son, He took the demon's dead body, which was in the shape of a conchshell, and went with Balarāma to Samyamani, the residence of Yamarāja. Upon arriving at Yamarāja's abode, Kṛṣṇa blew on His conchshell.
Hearing the vibration, Yamarāja appeared and received Kṛṣṇa and Balarāma with respectful obeisances and elaborate worship. Yamarāja then said, "O Lords, what shall I do for You, who are playing the part of ordinary humans?" Lord Śrī Kṛṣṇa asked Yamarāja to return His teacher's son, and this was immediately done. Then Kṛṣṇa and Balarāma brought the boy back to his father.