In His appearance as a fish, the Lord protected Satyavrata Manu, the earth and her valuable herbs. He protected them from the waters of annihilation. As a boar, the Lord killed Hiraṇyākṣa, the son of Diti, while delivering the earth from the universal waters. And as a tortoise, He lifted Mandara Mountain on His back so that nectar could be churned from the ocean. The Lord saved the surrendered king of the elephants, Gajendra, who was suffering terrible distress from the grips of a crocodile.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
गुप्तोऽप्यये मनुरिलौषधयश्च मात्स्ये क्रौडे हतो दितिज उद्धरताम्भसः क्ष्माम् । कौर्मे धृतोऽद्रिरमृतोन्मथने स्वपृष्ठे ग्राहात्प्रपन्नमिभराजममुञ्चदार्तम्
gupto'pyaye manurilauṣadhayaśca mātsye krauḍe hato ditija uddharatāmbhasaḥ kṣmām | kaurme dhṛto'driramṛtonmathane svapṛṣṭhe grāhātprapannamibharājamamuñcadārtam
SB 11.4.18