Battle at Sea: The Power Unleashed!

is episode 173 of the original Naruto anime.

Synopsis
The Nine-Tails within Naruto helps beat Amachi. Although Amachi is quickly defeated and captured, the Sea Boss threatens to attack Naruto. Naruto summons Gamabunta and defeats it by evaporating its nucleus. Isaribi realized what Naruto said was right and that he did understand her because Naruto was also treated as a monster and with his help, Isaribi was happy. Afterward, Isaribi decided to go to Konoha in the hopes that Tsunade can cure her.