The Aqua Ruins are the centre of the Water Elemental Disorder. They are located in Tsunami Trough in the middle of the ocean.
Before Evann and his team investigate the ruins as part of their effort to counteract the Elemental Disorder, Jaid visits Tsunami Trough as a knight for the Arcadian people. He swore an oath to a noble lady that he would protect her but, during his absence in service to his country, the lady perished as a result of the Water Elemental Disorder. Jaid believes he can regain some honour by defeating this disorder with his own hands and therefore insists that he joins Evann on this mission.
The party reach Tsunami Trough by means of a Nortis ship and are lowered into the sea in a cage. In order to breath underwater, they all consume the Aeolus Seed provided by the Hazman people. However, during their descent, the ship above is toppled by the strong storm and waves and the chain is severed. The cage falls to the sea floor and the party must walk along the sea bed on foot to the ruins. The party reaches an ocean cave and finds a temple within. At the heart of this temple is an energy conversion room, which is whipping up the water into a great whirlpool. In order to stop this whirlpool, the guardian of the temple must be defeated. The guardian is a giant squid-like creature called the Deava.
Underneath this room is the Spiritual Atrium containing a crystallised elemental beast and the Water Slab.