Matsya Purana — Description of Gomedaka and Puṣkara Dvīpas; the Lokāloka Boundary; Ocean Tide...
क्षयवृद्धी समुद्रस्य शशिवृद्धिक्षये तथा दशोत्तराणि पञ्चाहुर् अङ्गुलानां शतानि च //
kṣayavṛddhī samudrasya śaśivṛddhikṣaye tathā daśottarāṇi pañcāhur aṅgulānāṃ śatāni ca //
They declare that the ocean’s ebb and flow correspond to the moon’s waxing and waning; and that the measure involved is five hundred and ten aṅgulas.
It does not describe Pralaya directly; instead, it links the ocean’s periodic increase and decrease to the moon’s waxing and waning, presenting a regular cosmic rhythm rather than dissolution.
By emphasizing predictable lunar-linked cycles and standard measures, it supports timing and planning—useful for calendrical observances, agriculture, and public works that a king or householder would schedule according to lunar periods.
The verse gives a concrete metrological figure (510 aṅgulas), aligning with the broader Purāṇic concern for exact measures—relevant for ritual spacing and, by extension, for Vāstu-style proportional planning where aṅgula-based units are foundational.