Matsya Purana — Description of Gomedaka and Puṣkara Dvīpas; the Lokāloka Boundary; Ocean Tide...
अपां वृद्धिः क्षयो दृष्टः समुद्राणां तु पर्वसु द्विरापत्वात् स्मृतो द्वीपो दधनाच्चोदधिः स्मृतः //
apāṃ vṛddhiḥ kṣayo dṛṣṭaḥ samudrāṇāṃ tu parvasu dvirāpatvāt smṛto dvīpo dadhanāccodadhiḥ smṛtaḥ //
An increase and a decrease of the waters is observed in the oceans at their ‘parvas’ (periodic junctures). Because it is ‘twice-watered’ it is called a dvīpa (island/continent); and because it bears and holds the waters, it is called the odadhi (ocean).
It does not describe Pralaya directly; instead, it notes a regular, cyclical waxing and waning of ocean waters at specific ‘parvas’ (periodic junctures), reflecting a Purāṇic view of rhythmic natural order rather than total dissolution.
Indirectly, it supports the dhārmic ideal of governance and household life aligned with ṛta (cosmic order): understanding seasons, cycles, and natural boundaries (land and sea) is part of prudent administration, travel, and settlement planning described across Purāṇic instruction.
No explicit Vāstu or ritual rule is stated, but the verse’s focus on land surrounded by water (dvīpa) and the ocean as a ‘holder’ supports the broader Vāstu concern with site geography—water presence, boundaries, and natural cycles—when evaluating habitable regions.