"The Young Man and the Sea" (青年と海, Seinen to Umi) is episode 223 of the Naruto: Shippūden anime.
Tsunade sends Naruto to the Land of Lightning under the guise of an S-rank mission to keep him hidden away from the Akatsuki. Naruto leaves Konoha with Aoba, Yamato, Guy, and three unknown shinobi. However, they find themselves held up at port due to a report of a monster attacking ships, making people afraid to set sail. When Guy and Aoba go out to see if they can solve the problem, they encounter an aggressive giant marlin, as well as a fisherman named Yūsuke. Yūsuke notifies them that the marlin has been in their waters for fifteen years and is responsible for the death of his father, and wishes to avenge him. In order to help him on this quest, Yamato uses his Wood Release to fashion a boat and a fishing pole with Guy providing rowing power, tapping into his Eight Gates to keep up with the marlin.
Yūsuke manages to tire out and defeat the marlin, considering his vengeance to be complete. The jōnin wonder why the marlin, believed to be a summon cast by a shinobi during the Third Shinobi World War, has not dispelled itself yet. Naruto notices a Fūma Shuriken embedded near its head and pulls it out. No longer in pain, the marlin dispels itself home. The crew and fishermen of the port are free to sail once more; as Naruto heads to the Land of Lightning, he waves Yūsuke goodbye.