Srimad Bhagavatam Canto 08, Chapter 24, Text 44

SB 8.24.44

so ’nudhyatas tato rajña
 pradurasin maharnave
eka-srnga-dharo matsyo
 haimo niyuta-yojanah
 
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
 
Then, while the King constantly meditated upon the Supreme Personality of Godhead, a large golden fish appeared in the ocean of inundation. The fish had one horn and was eight million miles long.
Srimad Bhagavatam Canto 08, Chapter 24, Text 43
Srimad Bhagavatam Canto 08, Chapter 24, Text 45