Mercay Island

Mercay Island is a large island in the southeastern Great Sea and the first island Link visits in The Legend of Zelda: Phantom Hourglass. The island is home to a small port town with several houses, a shop, a Milk Bar, a beach, a small shipyard, and the port itself. Separating the eastern half of the island from the western half is a small waterfall crossed by a bridge (although the bridge was frequently knocked down by earthquakes). On the top of the island is an underground passage leading to the other side of the island, and more importantly the Temple of the Ocean King.

Secrets of Mercay Island
Many secrets aside in Mercay Island. One of them is, in the Temple of the Ocean King, you can talk to the spirits of the dead adventurers. Also, outside the temple, there is a crack in the wall, which you can bomb using either bombs or bomchus, then go inside, and get a chest. If you come back later, you can shoot the eye with an arrow to open a bridge, and then defeat the Zola (use the Hammer full charged for and easy win), and leave, you can read the tablet that says:

Then, go up the stairs and shoot the eye on the wall to get the Beam statue. hit the statue to shoot the beam and click it to aim it. Aim the one to the right of the Temple of the Ocean King, and bomb where the beam is. Then you can meet Freedle and use Wireless Tag Mode, which allows you to Trade Ship Parts and Treasures by putting the item in the Drum boxes. You can also trade ship parts via Battle Mode.