|Chapter 10, Verse 31|

पवनः पवतामस्मि रामः शस्त्रभृतामहम्।

झषाणां मकरश्चास्मि स्रोतसामस्मि जाह्नवी।।10.31।।

ॐ

Transliteration / Meaning

pavanaḥ pavatām asmi rāmaḥ śhastra-bhṛitām aham
jhaṣhāṇāṁ makaraśh chāsmi srotasām asmi jāhnavī

Translation

Of purifiers I am the wind, of the wielders of weapons I am Rama, of fishes I am the shark, and of flowing rivers I am the Ganges.

Purport by Srila Prabhupada

Of all the aquatics the shark is one of the biggest and is certainly the most dangerous to man. Thus the shark represents Krishna.