Giant Marlin

This Giant Marlin was once a summon during the Third Shinobi World War who for some reason, did not return to its birthplace.

Background
After the war, it stayed at the Land of Fire's harbour, attacking any boats in open water. Yūsuke and his father tried to catch it, but failed and resulted in Yūsuke's father's death.

Abilities
The marlin possessed a large sword-like appendage at the end of its snout. The sword was capable of injuring Might Guy in their initial confrontation and it appears to be as equally dense as the wood created by Yamato's Wood Release: Great Forest Technique. The marlin was extremely fast and could maintain its top speed for an extended period of time. Might Guy was forced to open five of the Eight Gates in order to row fast enough to keep up with the marlin.

Adventures at Sea Arc
When Naruto Uzumaki, Aoba Yamashiro, Might Guy and Yamato set sail to the Land of Lightning, they suddenly encounter the Giant Marlin who attacks and destroys their ship. Soon after they meet a young man named Yūsuke who is trying to catch the marlin. That night Yūsuke explains to the team that he needs a proper boat and rod in order to catch the marlin, maintaining stubborn intentions of catching it on his own. The next day they take Yūsuke with his equipments needed to capture the marlin, courtesy of Yamato's Wood Release, avenging his father. After locating the marlin they then commence the chase, and at last Yūsuke catches the marlin after exhausting it. Naruto finds a fūma shuriken on its forehead and pulls it out. Soon after, the marlin returns home.