Matsya Purana — Nārāyaṇa as Haṃsa in the Cosmic Ocean: Vedic Yajña-Puruṣa and Mārkaṇḍeya’s Vi...
निष्क्रम्याप्यस्य वदनाद् एकार्णवमथो जगत् सर्वतस्तमसाच्छन्नं मार्कण्डेयो ऽन्ववैक्षत //
niṣkramyāpyasya vadanād ekārṇavamatho jagat sarvatastamasācchannaṃ mārkaṇḍeyo 'nvavaikṣata //
Even after emerging from His mouth, Mārkaṇḍeya beheld the world as a single ocean (ekārṇava), veiled on every side by darkness.
It portrays pralaya as an ekārṇava—one boundless flood-ocean—where the manifested world is no longer differentiated and is obscured by pervasive darkness.
Indirectly, it underscores impermanence: worldly order can be withdrawn in pralaya, so kings and householders should ground their duties (dharma, charity, restraint) in lasting spiritual aims rather than temporary power or possessions.
No direct Vāstu or ritual rule is stated; the takeaway is symbolic—ritual and sacred architecture aim to establish light, order, and orientation against the cosmic imagery of darkness and dissolution.