Slayers: Knight of the Aqualord  

Slayers: Suiriyuuou no Kishi, Sui-Ryu-Oh no Kishi, スレイヤーズ水竜王の騎士

Lina and her companion are separated from each other, and Lina finds herself in an unfamiliar location outside of the mazoku barrier. There, she encounters a young boy named Lyos who is known as the Knight of Aqualord. Eventually, Lina is reunited with Gourry, and Ameria appears. Their mission is to seek out the power of the gods, but they soon encounter Riskfalto, the general of the Deep Sea Dolphins, who will lead them into a battle between divine beings and malevolent spirits.