At that time when the three worlds were submerged in water, Garbhodakaśāyī Viṣṇu was alone, lying on His bedstead, the great snake Ananta, and although He appeared to be in slumber in His own internal potency, free from the action of the external energy, His eyes were not completely closed.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
उदाप्लुतं विश्वमिदं तदासी- द्यन्निद्रयामीलितदृङ्न्यमीलयत् । अहीन्द्रतल्पेऽधिशयान एकः कृतक्षणः स्वात्मरतौ निरीहः
udāplutaṃ viśvamidaṃ tadāsī- dyannidrayāmīlitadṛṅnyamīlayat | ahīndratalpe'dhiśayāna ekaḥ kṛtakṣaṇaḥ svātmaratau nirīhaḥ
SB 3.8.10