Matsya Purana — Paurava Genealogy
स्कन्नं रेतः सत्यधृतेर् दृष्ट्वा चाप्सरसं जले मिथुनं तत्र संभृतं तस्मिन्सरसि संभृतम् //
skannaṃ retaḥ satyadhṛter dṛṣṭvā cāpsarasaṃ jale mithunaṃ tatra saṃbhṛtaṃ tasminsarasi saṃbhṛtam //
Seeing the fallen semen of Satyadhṛti, and seeing the apsaras in the water, the pair came together there; and in that lake their union was consummated.
This verse does not describe pralaya; it presents a mythic-generative motif (seed, union, and conception) used in Purāṇic storytelling to explain origins within a lineage or episode.
Indirectly, it reflects the Purāṇic concern with progeny and continuity of lineage; later ethical framing in the Purāṇa typically treats sexuality and progeny within dharma, though this specific verse is narrative rather than prescriptive.
No vastu/temple-building or ritual procedure is stated here; the setting (a lake/water) functions as narrative scenery for the episode rather than a technical ritual or architectural instruction.