Avatāra-kathā — The Puruṣa, the Many Incarnations, and Kṛṣṇa as Svayam Bhagavān
रूपं स जगृहे मात्स्यं चाक्षुषोदधिसम्प्लवे । नाव्यारोप्य महीमय्यामपाद्वैवस्वतं मनुम् ॥ १५ ॥
rūpaṁ sa jagṛhe mātsyaṁ cākṣuṣodadhi-samplave nāvy āropya mahī-mayyām apād vaivasvataṁ manum
Когда после эпохи Чакшуша Ману разразился вселенский потоп и весь мир погрузился в воды, Господь принял образ Рыбы (Матсьи) и спас Вайвасвату Ману, удержав его на лодке.
According to Śrīpāda Śrīdhara Svāmī, the original commentator on the Bhāgavatam, there is not always a devastation after the change of every Manu. And yet this inundation after the period of Cākṣuṣa Manu took place in order to show some wonders to Satyavrata. But Śrī Jīva Gosvāmī has given definite proofs from authoritative scriptures (like Viṣṇu-dharmottara, Mārkaṇḍeya Purāṇa, Harivaṁśa, etc.) that there is always a devastation after the end of each and every Manu. Śrīla Viśvanātha Cakravartī has also supported Śrīla Jīva Gosvāmī, and he (Śrī Cakravartī) has also quoted from Bhāgavatāmṛta about this inundation after each Manu. Apart from this, the Lord, in order to show special favor to Satyavrata, a devotee of the Lord, in this particular period, incarnated Himself.
Bhāgavatam 1.3.15 states that during a great deluge in the Cākṣuṣa era, the Lord assumed the form of Matsya and protected Vaivasvata Manu by placing the earth upon a boat.
Vaivasvata Manu is the progenitor for the next manvantara; by saving him, the Lord preserves humanity, dharma, and the continuity of creation after cosmic devastation.
It teaches trust in divine guardianship: even amid overwhelming “floods” of crisis, one can hold to dharma and take shelter of the Lord, who protects sincere seekers and preserves what is essential.