The Octonauts and the Poisonous Mermaid Spell

The Octonauts and the Poisonous Mermaid Spell is the 24th episode of Season 4.

Summary
Kwazii is cursed by a Poisonous Mermaid while collecting pearls and rubies in her lair he thought was an ordinary cave for his sister and falls into a deep sleep. So Peso and Barnacles go into the Midnight Zone to find the rarest kelp, the Black Kelp, to cure Kwazii before he sleeps forever.