Pradyumna is the name of a character in the Srimad Bhagavatam. He was the son of Lord Krishna and Rukmini. Pradyumna is considered as one of the four vyuha avatar of Vishnu. When he was a baby he was abducted by the demon Sambara. He was then cast into the sea and swallowed by a fish, but that fish was caught and carried to the house of Sambara. The fish was opened and the child was found inside.