Oxyale

Oxyale is an item in Final Fantasy that is used for the warrior to breathe underwater to explore the water shrine. To obtain the item, you must buy the bottle at the Caravans (for 50,000 Gil) and go to Gaia. Once in Gaia, you're going to have to go through its maze-like wooded back area. You should eventually find a pond. Stand by the pond and use the bottle. A fairy will appear and give you Oxyale to put in your bottle.