Betrayed

S1 E25: Behind Sirena and Lyla's backs, Nixie helps Cam get into the Moon Pool to unlock the Trident. But Evie insists on coming along for the dive. When the Moon Pool entrance suddenly closes, Evie is trapped underwater with her oxygen running out! Zac and the other mermaids come to rescue Evie, and their true mermaid identities are revealed to her. Meanwhile, Cam escapes with the Trident.