When even Parasurama could not vanquish Bhishma, a dejected Amba who wanted revenge against the person who had forcibly abducted her and then left her in the lurch, did severe penance in several holy places.
When she performed her penance on the banks of River Ganga, the goddess appeared before her and asked what she wanted.
Amba narrated her tale to Ganga and asserted her desire to kill Bhishma.
The River Goddess became furious on hearing Amba’s words and cursed her, “Your thoughts are crooked. May you be born a crooked river, infested with crocodiles and unfit for the performance of religious rites.”
When Amba reached the holy spot called Vatsabhumi, half her body became a crooked river, filled only during rain, inaccessible and full of crocodiles.
It was thanks to the merits she had accumulated by her penances that the other half of her body helped her retain her maiden form.