He outwitted the Vindhya mountain when, in its pride, it tried to obstruct the natural path of the sun. He drank all the waters of the ocean to expose the wicked Kalkeyas, who hid there after challenging the Gods to battle.
Agastya is the most well-known among the Saptarshi. His stories are found not just in the Vedas but are scattered through the Brahmanas and the Puranas as well. These stories are known not only in India but are also a part of S.E. Asian mythology.