The story of Pisces:

Pisces represents the goddess of love & beauty, Aphrodite and the God of love Eros. While taking a stroll down the Euphrates River, they had an encounter with the vicious Typhon. They pleaded to Zeus to help them escape, so Zeus changed the two into fish and they swam away to safety. In remembrance of this, Athena placed the twin fishes amongst the stars.