Somewhere travelling across the sea aboard a boat known as The Floating Palace, Sofia is in the library reading a story when the royal family arrives at a tropical island known as Merroway Cove for a vacation. When Sofia asks if they'll meet any mermaids, Roland and Admiral Hornpipe both tell her mermaids are not real but there have long been tales when Roland was still a little prince. Also accompanying the Royal family is Cedric who is out on another scheme to take over Enchancia only this time he's not after the Amulet of Avalor. He is in search of a mystical object known as the Mermaid Comb of Merroway Cove, that gives whoever possesses it really strong hydrokentic powers. He takes a boat to a cave and transforms himself into a sea monster and Wormword into a squid.
Meanwhile, Sofia meets up with Clover and head down to the swimming platform. Once there, they spot a Mermaid who gets trapped in a net. Sofia pulls her onto the platform and helps her get untangled. Once free, Sofia introduces herself to the mermaid who introduces herself as Oona and the two girls become fast friends. Oona is amazed by the floating palace which was why she came up to get a closer look. She notices Sofia's amulet glowing and when she asks her about it, Sofia tells Oona it’s enchanted. Oona tells her that the comb she's wearing is enchanted as well, but doesn't know what powers it possesses because her mother refuses to tell her as she is not old enough yet. After she gets back in the water, Oona discovers her fin was injured by the net. Sofia takes off her shoes so she can put her feet in the water and help her. The moment her feet makes contact with the water, she transforms into a mermaid. Remembering the glow her new friend saw earlier and the rule about the amulet, Sofia tells Oona her amulet gives her special powers when she does good deeds. Since she helped her when she was in trouble, her amulet blessed her with the ability to transform into a mermaid. All this makes Sofia squeal "I can swim in the water like a mermaid!" and happily hops into the water. She drifts down a few fathoms until she opens her eyes and squeals "This is incredible!" and starts swimming at lightning speed before returning to the surface. With the use of her new abilities, Sofia helps Oona swim home. Meanwhile, Clover meets a sea gull named Farley who tries to make off with a bag of blueberries that Clover marked as his. A battle erupts between them that causes the blueberries to get spilled overboard and gets them both stuck in a lifesaver.
Meanwhile, Sofia takes Oona to the bottom of the cove and all the sights make Sofia squeal with delight. The two girls enter a shipwreck that Oona uses as her hideaway. Suddenly a seahorse appears and calls out for Oona who tries to hide Sofia. She tells Sofia that seahorse is her friend Sven who gets very suspicious around strangers. Sven finds the two girls and then asks Oona about where she’s been and who her new friend is, stating he hasn't seen her in the cove before. Oona says Sofia is visiting from another colony and when she hurt her fin she helped her get back. When he hears this, Sven panics and says Oona needs to see the doctor right away just as an older mermaid shows up, asking "See the doctor about what?" After being told about Oona's hurt fin, the mermaid proceeds to examine her fin: It turns out her injury is so minor it can be treated by bandaging it with some moon kelp. Oona introduces Sofia to the mermaid who happens to be her big sister Cora, who was sent by their mother to check on her. After Cora bandages her fin and leaves, Oona begins to moan about how her sister treats her like a merbaby, which Sofia understands completely as she knows how it feels. Then she asks where the other merfolk live and, through a song, Oona and Sven give her a tour of the cove.
Unbeknownst to Sofia, she and Oona are being watched by Sea Monster Cedric and Wormwood the Squid who recognize Oona's comb as the mystical item they seek. When he spots Sofia, he mutters in shock that with her around she will ruin his chances of getting the comb. Suddenly, the floating palace appears from above and Cora shows up to tell Oona their mother wants them back at the castle. Sofia follows the two mermaids to the coral castle where she meets Oona's mother, Queen Emmaline of Merroway Cove and her chief advisor, Plank. It turns out that the merfolk think humans are dangerous because many years ago, a pirate ship entered the cove and tried to capture one of the colony's inhabitants and most of its people were hurt which is the reason they avoid going to the surface and the ship in question is the same shipwreck Oona uses as her hideaway. Plank proposes that Queen Emmaline move the ship from the cove by conjuring a storm with her Trident. Cora is the only one who supports this decision but Sven and Queen Emmaline view the plan as too reckless and irresponsible because it might sink the ship. Knowing her family is on that ship, Sofia is immediately against this plan and insists on a peaceful alternative. She tells Plank and Queen Emmaline that she will go up and persuade them to move the ship. When Queen Emmaline and Plank both ask her how she would do that since she's a mermaid, she reveals herself to be a human who has transformed into a mermaid and that ship belongs to her family. The entire mercolony is shocked except Oona who knew the whole time. When Plank and Cora start acting negatively towards her both Oona and Sven swim forward and defend her by telling everyone how she helped Oona when she was hurt. Sofia gives the Mermaid Queen her word that she will get the ship to move and after being commanded by Queen Emmaline never to return afterwards, she agrees to her wishes and sadly bids her friend farewell before leaving.
Oona goes after Sofia and apologizes for how everyone acted. Sofia shrugs it off as nothing and gives her a loving hug before sadly continuing to head back to the ship. But then trouble erupts for both girls: Just as Oona starts to head back home Sea Monster Cedric appears and attacks her. As Sofia is about to climb back on board, she hears Oona calling for help and dives back into the ocean to help her. Oona heads into the kelp forest but gets ambushed by Wormwood the Squid and Cedric captures her. Sofia finally arrives in the kelp forest and calls out for Oona but to no avail. Realizing the monster must've kidnapped Oona, Sofia heads back to tell Queen Emmaline what happened. However, nobody believes her, especially not Plank. He accuses her family of kidnapping Oona and urges Queen Emmaline to use her trident to conjure a massive storm that will sink the floating palace. Convinced that Plank is right, Queen Emmaline gives Sofia until sundown to return her daughter and prove her family's innocence or she'll use her trident to do as Plank suggested. Sven chooses to accompany Sofia because he knew she was being sincere the whole time.
On the ship, it turns out the family hasn't even noticed that Sofia is gone and are only just now noticing but they all assume that she's in her room finishing her book. When Sofia gets back on board, she heads to her family and Admiral Hornpipe to tell them about Oona's kidnapping and her mother's threat to sink the floating palace. Unfortunately like the merpeople, they don't believe her and with no one else to turn to Sofia now believes its up to her to find and rescue Oona. She frees Clover and Farley from the lifesaver and instructs the seagull to take to the skies and look for Oona. He finds her locked in a cage on the monster's boat and goes back to tell Sofia. The three of them find the cave and find out the monster wants Oona's comb. Sofia tries to rescue her but the sea monster is too powerful for her which gives her no choice but to retreat.
Sofia feels like all hope is lost: she failed to rescue Oona and knows the second the monster gets her comb there will be no telling what he'll do to her mermaid friend and her family will be drowned for a crime they never committed, all because no one believes her. Sven suggests going back to tell Emmaline they found Oona but Sofia refuses stating that it's a waste of time. Suddenly Sofia's amulet begins to glow summoning Princess Ariel. Through a song, Ariel tells Sofia she still has a chance to save Oona by enlisting Cora to help by showing her that she cares about Oona as much as Cora does. Soon after Ariel vanishes, Sofia manages to convince Cora to help her and the two princesses head off to the rescue.
Meanwhile, Queen Emmaline uses her trident to conjure up a storm until Sven and his family intervene before it gets too fierce. With the trident in their possession, they lead Emmaline and Plank to where Oona is being held. With Sofia and Cora working together, they successfully rescue Oona and defeat Cedric with the power of Oona's comb. The two mermaids are reunited with their mother and Plank who both apologize to Sofia for their rashness and using the trident, Emmaline stops the storm. While she does this, she is seen by Sofia's family and Admiral Hornpipe who stare in amazement, realizing that Sofia was right all along. Sofia heads back to the ship and happily reunites with her family who all apologize for not believing her. Then she takes them to meet the merfolks who all become good friends with them and Sofia and Oona are allowed to remain friends forever. Meanwhile, a defeated Cedric returns to the Floating Palace and turns himself and Wormwood back to normal.
Home Video Release
- Ariel Winter as Sofia
- Sara Ramirez as Queen Miranda
- Wayne Brady as Clover
- Tim Gunn as Baileywick
- Darcy Rose Byrnes as Princess Amber
- Zach Callison as Prince James
- Travis Willingham as King Roland II
- Kiernan Shipka as Oona
- Jodi Benson as Ariel / Queen Emmaline
- Jeff Bennett as Farley
- John Ross Bowie as Sven
- Phil Morris as Plank
- Sarah Mitchell as Cora
- Jess Harnell as Cedric the Sorcerer
- Jim Cummings as Wormwood / Admiral Hornpipe
- This is the second time a Disney Princess shows up in a special (Cinderella) and the second special of the show (Sofia the First: Once Upon a Princess). There are also similarities especially between these two meetings:
- Sofia covers her eyes in despair seconds before her amulet glows and a glow is seen where the summoned princess will appear.
- Both state that the amulet summoned them to help.
- The princesses (Sofia and the summon) take a stroll (or a swim) in both cases.
- The meetings include a musical number, and both hint on what Sofia should do to set things right and the one person (Princess Amber and Cora) she should converse with to get started.
- The strolls end in a doorway to a "room" where an older girl is sulking (Princess Amber and Cora).
- In the last word of the musical number the summoned princess and Sofia are in the same position in both cases, with Sofia facing the doorway and the princess right behind her, hands rested on the former's shoulders and as Sofia turns round to thank her, the princess had magically disappeared leaving behind a cloud of shimmering stars.
- As Sofia meets the girl, they respond negatively at first until Sofia declares her mission to her. Both missions also involve a confrontation with Cedric or at least Wormwood with both girls working together.
- This is the second time Sofia undergoes a magical transformation. In "Cedric's Apprentice", she became a lizard.
- This is the second time Sofia strengthens ties between her family and supernatural creatures. Before, it was the trolls in the episode "Let The Good Times Troll".
- Ariel is the fourth Disney Princess to assist Sofia.
- Ariel is the first princess to not to be seen in her redesign as she was in her mermaid form.
- When Oona asks what kind of animal Clover is, he says "I'm a Blue Ribbon Bunny," a reference to the song and the seventh episode.
- Oona, in many ways, is similar to Sofia. Both are princesses who are the youngest members of a Royal family and possess a mystical object which gives them magical powers.
- The timeline of the series seems to be falling into a year since Sofia became a princess. Jade stated in "The Little Witch" that Lucinda arrived a few months after Sofia left. "Princess Butterfly" took place on Halloween, "Great Aunt-Venture" in November (most likely) and now a vacation, followed by winter holidays
- This is the second episode where Cedric doesn't go after the Amulet, the first episode was "Tea for Too Many".
- Cedric undergoes a magical transformation for the first time in the series and so does Wormwood.
- This is Cedric's last appearance in the first season.
- This is the only episode where James is seen shirtless.
- Oona is the only one Sofia tells about her amulet.
- Oona and Sven are the only ones who know the truth of Sofia's Amulet. Queen Emmaline, Plank, Cora, and the other merfolk are aware of Sofia's powers but not the source.
- This is the second time Sofia's amulet grants her a blessing. The first was Sofia the First: Once Upon a Princess.