While visiting her cousin Cristóbal, Elena meets mysterious underwater creatures called Sirenas and encounters the evil sorceress Shuriki.

"The Princess in Black and her friends are enjoying a day of sun and sea on Princess Sneezewort's royal boat when a real, live mermaid princess emerges from the waves! Eeeeeee! Princess Posy needs their help protecting her very cute sea goats from being eaten by a very greedy kraken. But the princesses and the Goat Avenger quickly realize that fighting underwater can be tough for land dwellers, and only the mermaid Princess Posy can save the day....

Four children set out to capture a mermaid, but she manages to escape all of their traps.

When third-grader Shelly Siren finds out she is a real princess she starts to wonder if she should act differently.

When she incurs Neptune's wrath by finding a diamond ring buried under rocks in the ocean, Emily is put under a curse that will force her to choose to be either a mermaid or a human and split up her parents forever.

When young Pearl, a mermaid, becomes caretaker of a single grain of sand, she discovers that performing even the smallest task well can transform the world.

Merliah discovers she is a mermaid princess and must go to Oceana to rescue her mother from the evil Eris.

The wicked Mantora sets another trap for the young mermaids by littering a beach where a seal family lives, and Scarlett's bossiness interferes with the clean-up effort, further delaying the mission to bring the magic crystals home.

Three fairies from Never Land must deliver a wand they promised to the mermaid who has threatened to flood their home in Fairy Haven.

Neptune, King of the ocean, sends half-mermaids Emily and Aaron to the land of the midnight sun to investigate the source of the dangerous storms brewing in the ocean.