Aquata Returns is the twenty-first episode of Mako Mermaids. Aquata returns and informs Sirena that she, but not Lyla or Nixie, can return to the pod. The mermaids now seize the Trident and conceal it. After viewing Aquata, Zac believes the mermaids are requesting reinforcements in order to reclaim the trident. He refuses and states that no one will help them unless they prove themselves worthy by fighting Anki. The next day, the mermaids battle Anki again but fail to defeat him. Furious, Lyla challenges him to a fight. During the fight, it is revealed that Lyla is actually a hybrid between a human and a mermaid. Nixie attempts to attack Anki with a boulder but fails. Anki then uses this opportunity to crush her skull. Meanwhile, Sirena confronts Aquata about whether or not Lyla and Nixie can return to the pod. Aquata explains that since Lyla is half-human she cannot go back into the water without dying. This causes Sirena to question why she was brought back in the first place if she cannot return to the pod. Aquata tells Sirena that she was needed outside of the pod for a special mission. When this mission is completed, she will be returned to the pod. Later that night, the mermaids hear something approaching their island. It turns out to be a large ship that sinks soon after arriving at its destination.