From Final Fantasy Wiki

Barwater is a White Magic spell found in Final Fantasy XI. It can be learnt by Red Mages at level 9. When cast, the spell increases the player's resistance to Water, increasing the likelihood that the player will resist Water-based spells and attacks. It may be recast every 10 seconds for 6 MP, and, like all Enhancing magic, its effectiveness changes depending on the player's Enhancing Magic skill. Those playing as White Mages have access to an upgraded version, Barwatera.