Tetra

Character in The Wind Waker
The pirate who was kidnapped by the Helmaroc King early in the Wind Waker. When the bird is shot, she falls into the forest, and the Helmaroc King takes Aryll, mistaking her for the pirate.

In her room in the pirate ship, there is a picture of the Royal Family including Princess Zelda and a band of people that look closely related to the pirates on board. This picture and others also hang from the walls in Hyrule Castle which Link visits during Wind Waker. It is later revealed that Tetra is in fact a descendant of the Zelda bloodline, making her Princess of Hyrule which in her time, is still flooded deep under the Great Sea.

As Zelda, she later aids Link in the final battle against Ganondorf, wielding Link's bow and firing Light Arrows at the fiend.

After Hyrule's final end, Link and Zelda, once more in the guise of Tetra, float to the surface and reunite with Tetra's pirates, sailing away to find a new land to call their own.

Character in Phantom Hourglass
In Phantom Hourglass, she and Link happen upon a Ghost Ship, which they investigate. Tetra is separated from the others and is summarily kidnapped, forcing Link to try and rescue her.

After Link defeats Bellum, he and Tetra awaken on the Ghost Ship, only ten minutes after the prologue according to the pirates. Tetra's crew tries to convince her that it was just a dream, but Link finds the Phantom Hourglass in his pocket, and the S.S. Linebeck is seen sailing in the distance.

Notes about the Character

 * Tetra's name could be derived from the Latin meaning for 'four', similar to Tetris, this could hint at her being the fourth Zelda descendant in the timeline.
 * Tetra could also allude to tetrahedron, the physical shape of the Triforce.
 * A Tetra is also a type of South American freshwater fish, adding to the sea-faring theme of the game.
 * Tetra was introduced in the The Wind Waker and appears again in the Phantom Hourglass.
 * Although Tetra does not play a role in the game, she appears as a trophy in Super Smash Bros. Brawl.