Srimad Bhagvata Mahapurana: Book 10: Chapter 28: Verses 1-12
Sri Krsna rescues His father from the realm of Varuna
Sri Suka began again : Having fasted on the (following) Ekadasi (the eleventh day of a lunar fortnight) and duly worshipped Lord Visnu (who is solicited by His devotees and is the deity presiding over this day), Nanda descended into the water of the Kalindi (during the third watch of the night) in order to take his bath within the hours of the Dwadasi (the twelfth day). A demon servant of Varuna (the god of water) seized and took Nanda to the presence of his master on the plea of his (Nanda's) having entered the water at night, (apparently) not knowing that the hour is reserved for the (activities of) demons. Failing to perceive Nanda, the cowherds cried out, "0 Rama ! 0 Krsna !" Hearing the cry and coming to know of His father having been carried away to Varuna, the almighty Lord, who affords protection to His own, sought the presence of Varuna, 0 king ! Finding Sri Krsna (the Ruler of the senses) arrived at his door, Varuna (the guardian of a sphere), who was greatly rejoiced at His sight, worshipped Him with grand presents and spoke (as follows). Varuna said : It is today that my life has been fulfilled and it is only today that a (real) treasure has been found (by me), (even though I possess all the treasures of the world, being the lord of the ocean, a storehouse of all jewels), 0 my Master. (The end of my worldly existence also seems to be near inasmuch as) those worshipping Your feet have reached to the other end of their life's journey (viz., final beatitude).