With two crystals restored, your next target is the Water Crystal. This requires a special item: the Oxyale. To obtain the Oxyale, you must first awaken the Elf Prince in Elfheim (if you haven't already) and then visit the Northwest Castle. After obtaining the Oxyale, you can use your ship to sail to the Sunken Shrine, located in the middle of the ocean. The Sunken Shrine is an underwater dungeon, and the Oxyale allows your party to breathe. Be prepared for water-based enemies and a labyrinthine layout.
