Valmiki Ramayana Sundara Kanda Sarga 43 Shloka 15
Original Shlokaआवर्त इव गङ्गायास्तोयस्य विपुलो महान्। परिक्षिप्य हरिश्रेष्ठं स बभौ रक्षसां गणः।।5.43.15।।
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सः that, रक्षसां गणः horde of ogres, हरिश्रेष्ठम् best of vanaras, परिक्षिप्य having surrounded, गङ्गायाः of the river Ganga, तोयस्य of the water, महान् huge, विपुलः big, आवर्त इव like a whirlpool, बभौ looked.
The demons surrounding the great monkey looked like a big whirlpool of the water of the river Ganga.