Matsya Purana — Description of Gomedaka and Puṣkara Dvīpas; the Lokāloka Boundary; Ocean Tide...
एवं द्वीपाः समुद्रैस्तु सप्त सप्तभिरावृताः द्वीपस्यानन्तरो यस्तु समुद्रस्तत्समस्तु वै //
evaṃ dvīpāḥ samudraistu sapta saptabhirāvṛtāḥ dvīpasyānantaro yastu samudrastatsamastu vai //
Thus the continents (dvīpas) are enclosed by seven oceans, each in a set of seven; and the ocean that immediately follows (surrounds) a given continent is to be understood as corresponding to it in due order.
This verse is not about pralaya; it outlines the structured cosmography of the world—seven dvīpas arranged in order, each surrounded by an ocean—reflecting an ordered cosmic design rather than dissolution.
Indirectly, it supports the Purāṇic ideal that rulers and householders should understand cosmic order (loka-vyavasthā) and uphold harmony in their domains; it is descriptive geography rather than a direct dharma injunction.
No explicit vāstu or ritual rule is stated; however, Purāṇic cosmography often informs sacred layout symbolism (e.g., concentric planning in maṇḍalas and temple iconography), where ordered enclosures mirror cosmic enclosures.