Once Parashara rishi was travelling along the bank of river Yamuna, he met Matsyagandha, the beautiful daughter of a fisherman, Matsyagandha. Parashara rishi was infatuated by her beauty and wanted to be intimate with her. 

Matsyagandha pointed towards the people standing at the bank of river Yamuna and felt shame. Parashara rishi created an island in the middle of the river and covered it with fog. He also promised that her virginity would be restored. Lastly he converted the unpleasant fish smell into a beautiful flowery smell, making her Yojangandha. 

Eventually they became intimate. Satyavati gave birth to Parashara muni’s son on that island, who came to be known as Krishna Dwaipayana, because of being born into an island and his dark skin.

Matsyagandha was none other than Satyavati, who later married Hastinapur king Shantanu and was the grandmother of Dhritarashra and Pandu. The child of Satyavati and Parashara rishi was none other than Ved Vyas.