Captain Stalfos

is a boss in. He is the leader of the group of NaN Pirates. In order for Tingle to join the pirate crew, he has to be dead. If he wants to survive, he must defeat the captain in a sword duel. If Tingle succeeds in this task, he will be given the Bone Ocarina, which may be used at any pier to call the pirate ship.

Possessed Captain Stalfos
Later on, the captain gets possessed by insects from the Insect Cavern, and Tingle must calm him down in order to continue on his journey. To do this, he must surround the captain by pushing barrels of explosives around him, and then detonating them. If Tingle is successful, the crew of NaN Pirates will give him an upgraded Bone Ocarina, which can be played near one of ten pirate treasure chests to unlock it.

Trivia

 * The top screen displayed during this fight is a reference to the Arcade  titles, where the challenger and his opponent would be displayed with changing expressions based on their health.