Greatfish Isle

Greatfish Isle is an island of the Great Sea in The Wind Waker. Once the location of a peaceful village of Hyruleans and Jabun, it is now a horrific wreck after being demolished by Ganondorf. Jabun fled the island and headed for Outset Island. Now, the only residents are a Traveling Merchant and the Korok Linder. However, it still holds two Heart Pieces and is one of the recurring destinations of the Ghost Ship. One of the Pieces of Heart can be found in a small indent by flying with the Deku Leaf directly northwest from the small spiral island chunk atop where the Korok rests. The other Heart Piece is given to Link from the Merchant in exchange of the Shop Guru Statue.

Beneath the waves is a fragment of the Triforce, available after finding and opening the Triforce Chart from the Islet of Steel (which is located one square south).

Water Temple Theory
It has been speculated that Greatfish Isle was the original location of The Wind Waker's supposed Water Temple, because it was the home of Jabun, the keeper of Nayru's Pearl. Since the Great Deku Tree safeguarded Farore's Pearl, and the sky dragon Valoo protected Din's Pearl, it only makes sense for the home of Jabun to exist in a temple-bound place so he too can supervise the care and safeguarding of Nayru's Pearl. However, this theory has not been confirmed by Nintendo, and must therefore be taken as mere fan speculation.