Valmiki Ramayana Yuddha Kanda Sarga 59 Shloka 35

तान् them, सचिवान् counsellors, विसर्जयित्वा sent away, ततः there upon, रक्षःसु Rakshasa, यथानियोगम् as instructed, गतेषु having departed, वानरसागरौघम् ocean of Vanaras, महाझषः gigantic fish, पूर्णम् totally, अर्णवौघम् इव like the war in the ocean, व्यदारयत् pierced through.

After the counsellors departed from there Ravana pierced through the ocean of Vanaras just as gigantic fish would pierce in the sea.