Oona the mermaid is friends with everyone, but when her attempts to befriend a shark with sensory issues fail miserably she realizes what may be fun for her may be overwhelming for him.

Kiki Coral has an amazing gift: she can see the future. She doesn't have visions very often, but they are always surprising! When Kiki sees a vision of her classmate Rocky Ridge coming face-to-frightening-face with a gigantic leatherback turtle, she is frightened to the tip of her shiny purple tail. Can Kiki save Rocky from his dangerous fate? What if no one in Trident Academy believes her scary prediction?

Of all the creatures in the ocean, sea horses are Echo Reef's favorite. They're sweet and gentle and they glide through the water so gracefully. When Echo discovers that Rocky Ridge, one of her Trident Academy classmates, has his own pet sea horse, she wants one right away. Not everyone agrees sea horses should be pets, however. Perhaps they are happiest when swimming freely. But Echo thinks that if Rocky can make a sea horse happy, she can too! Can't...

Mermaid Echo is doing tail flips because she's going to see her favorite under-the-sea band, the Rays. They're performing for Pearl's birthday party and everyone at Trident Academy is invited except Echo's best friend Shelly.

"Pearl has always dreamed of being famous: the star-studded stage, the sea flowers, the applause! So when she finds out that her third grade class is performing The Little Human, she just knows she ll get the leading role. Especially since world-renowned merstar Angelfish Molie is judging the tryouts! But in a shocking turn of events, Pearl s best friend, Wanda, gets cast as the little human instead and Pearl is stuck playing the stinky sea witch....

"Shelly Siren and her friends visit King Neptune's royal castle and attend their first ball in this Mermaid Tales adventure" -- "Shelly, Echo, Kiki, and Pearl are spending their school vacation at Neptune's castle! Shelly's aunt, Queen Edwina, has invited the girls to stay for a whole week, and while they're there the girls can't wait to visit the Royal Orca Museum, see the Palace Library, ride seahorses, and maybe even attend a royal ball. Shelly...

Marnie competes against her friend Orla and Gilly, a new student at Lady Sealia Foam's Mermaid School, for the lead role of Queen Maretta in the annual Clamshell Show.

Cora the mermaid is having trouble with spelling, but if she wants to stay on the swim team she has get an A on her next test--so her mother gives her a "magic" diary that compels her to practice writing, while her friends explain to her the concept of studying.

When two of her Neptunia relay team members are injured and unable to swim in the thirteen-year-olds' race, Cora presses her friends Rachel and Shyanna into service--but when the team's lucky Sea Lion statue disappears Cora fears sabotage and sets out to find the guilty party, and her chief suspect is a merboy on the rival Titania team.

Rachel is new to the Kingdom of Neptunia, and she has two secrets--she is half human which only her friend Shyanna knows, and her boy friend is a human boy, Owen, who does not know know she is a mermaid.