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.

Adventures at Sea Arc
When Naruto Uzumaki, Aoba Yamashiro, Might Guy and Yamato set sail to the Land of Lightning, the marlin attacks and they meet Yūsuke, who is trying to capture the marlin. The next day, they help Yūsuke with his equipments needed to capture the marlin, avenging his father. After its capture, Naruto finds a fūma shuriken on its forehead and pulls it out. Soon after, the marlin returns home.

Powers and Abilities
The giant marlin posesses a large sword-like appenage at the end of it's snout. The sword was capable of injuring Might Guy in their initial conferntation and it appears to be as equally dense as the wood created by Yamato's Giant Forest Jutsu. The marlin is extremely fast and can maintain it's top speed for an extended period of time. Might Guy was forced to open his fifth inner gate in order to row fast enough to keep up with the marlin.