Rescuing Guru's Son

When Krishna and Balarama were requested by their teacher, Sandipani Muni, to bring back his son, they first approached the ocean where the boy had drowned and called for the deity of the ocean. The ocean deity told them that actually the boy was captured by a demon that resided deep in the water in the shape of a conchshell. Krishna dove into the water, caught hold of the demon, and killed him on the spot. But He did not find the boy within the demon's belly. Krishna took the demon's body (in the shape of a conch shell) with Him and He and Balarama went to the residence of Yamaraja, the superintendent of death. Yamaraja understood who the two boys were and he offered his services to Them. On Their request, Yamaraja returned the boy the Supreme Personality of Godhead, and Krishna and Balarama brought him to his father who was very happy and glorified Krishna and Balarama. - Summarized from Krishna Book, Chapter 45