You are now supposed to take Tetra to the place where you found the Master Sword. It is already opened so do not worry. Here you will learn a lot about your destiny. Also, you will learn that Tetra is Princess Zelda's daughter. The King of Red Lions is the King of Hyrule! This is getting very interesting now. Go back to the boat and learn about the Triforce of Courage. It was split into eight pieces. You must find all of those pieces. Now head up to the sea.