Srimad Bhagavatam Canto 10, Chapter 45, Text 37

SB 10.45.37

dvijas tayos tam mahimanam adbhutam
 samloksya rajann ati-manusim matim
sammantrya patnya sa maharnave mrtam
 balam prabhase varayam babhuva ha
 
Translation: 
 
O King, the learned brahmana Sandipani carefully considered the two Lords’ glorious and amazing qualities and Their superhuman intelligence. Then, after consulting with his wife, he chose as his remuneration the return of his young son, who had died in the ocean at Prabhasa.
 
Purport: 
 
According to Srila Visvanatha Cakravarti, the child was captured by the conchshell demon while playing at the Maha-siva-ksetra.
Srimad Bhagavatam Canto 10, Chapter 45, Text 35-36
Srimad Bhagavatam Canto 10, Chapter 45, Text 38