Kshirasagara | क्षीरसागर
Kshirasagara (Devanagari: क्षीरसागर ISO15919: kṣīrasāgara) is the ocean of divine milk. Lord Vishnu reclines on top of Shesh naag (divine servant with 1000 heads) in this ocean.
REFERENCE
Prema Rasa Madira - The Intoxicating Bliss of Divine Love, Vol. 3, Ch. 20