Daughter of the Deep is a 2021 middle grade science fiction and fantasy novel by Rick Riordan. This New York Times bestseller, in which Riordan draws influence from Jules Verne’s classics science fiction novels Twenty Thousand Leagues Under the Sea (1872) and The Mysterious Island (1875), is full of retrofuturistic action and adventure. Daughter of the Deep is also an IndieBound bestseller and Riordan’s eleventh book that received the Goodreads Choice Award for Middle Grade & Children’s books. As of early 2022, Riordan is in plans to adapt Daughter of the Deep into a film.

On her last day of freshman year at Harding-Pencroft Academy, Ana Dakkar goes for a swim with her older brother, Dev, and their dolphin friend, Socrates, while she waits to begin her freshman-year trials. Ana is in Dolphin House, known for its communication skills, whereas her brother is in Shark House, known for its warrior-like training. She later heads to the bus with her friend and roommate Ester, who is in Orca House, known for its focus on education and healing, and Nelinha, who is in Cephalopod House, known for its skills in engineering and technology. All of the freshman at HP Academy (as it is known for short) take a bus with their much-disliked Theoretical Marine Science professor, Dr. Hewett, to get to the ship where their trials will take place. On their way, however, they see HP Academy suddenly crumble into the ocean, destroyed by a torpedo that only Ana saw.

Dr. Hewett informs the students that their new priority is to protect Ana at all costs although he does not explain why. He also assigns Gem, a student in Shark House, to be Ana’s bodyguard. When they board their ship, the Varuna, they must leave at once to avoid danger. On board, Hewett explains to Ana and the other house prefects that Jules Verne’s novels were based in reality: Captain Nemo’s real name was Prince Dakkar, and Nemo left behind incredible and advanced technology. The true purpose of HP Academy is to guard these technological secrets and keep them from their rival school, the Land Institute (LI), which wants to use this “alt-tech” to control the world.

Then students from LI attack, capturing Ana and revealing that Hewett used to work at LI. They have come on the Aronnax, a submarine meant to supersede Nemo’s Nautilus. With Socrates’ help, Ana escapes. The students from HP find out from a captured LI student that Hewett came up with the idea for the Aronnax, and in response, Hewett tells Ana and her friends of the origins of the LI and HP Academies—the Land Institute for Ned Land, who along with Pierre Aronnax and Conseil (characters from 20,000 Leagues Under the Sea) founded the school, and Harding-Pencroft Academy for Cyrus Harding and Bonaventure Pencroft (from The Mysterious Island). Ana realizes that her friend Ester Harding is descended form Cyrus Harding, and Hewett reveals that Ana is descended from Prince Dakkar. Ana, who shares her ancestor’s DNA, is now the only one who can control Nemo’s technology. Hewett also reveals that Ana’s parents, who are dead, died discovering the long-abandoned Nautilus.

When Hewett, who has cancer, collapses, the HP students must make their way to the secret Lincoln Base, where the Nautilus is located, alone. Due to her legacy and relation to Nemo, Ana is reluctantly forced to take command. Ester feels guilty for keeping the origin of HP Academy a secret from her friends, and Ana feels guilty for her brother’s apparent death. When they reach the island, Ana and the other students pass a challenge in order to land, and there they meet former HP students Luca and Ophelia, as well as their companion, Jupiter, an orangutang who loves to cook and bake.

Ophelia and Luca reveal that they knew Ana’s parents, and they eventually show Ana to the Nautilus. Ana brings Nelinha and Ester, and Ester figures out that the Nautilus, which is in a state of disrepair, killed Ana’s parents because it was angry and neglected. The submarine, however, allows Ana to enter, and Ophelia and Luca show them around the magnificent ship. Later the rest of the students join and help with the repair efforts, which please the Nautilus. Suddenly, however, the Aronnax finds them.

Most of the students pilot the Nautilus away from the island, trying to protect the submarine and the base, although the Aronnax manages to track them. Then, Ana is horrified to hear Dev’s voice coming from the Aronnax, revealing that he is a traitor. The HP students manage to use the alt-tech on the Nautilus to escape, and while they work on repairing the submarine, Ana ruminates on her family’s and Nemo’s legacy. Ester also helps Ana discover Nemo’s treasury, which holds enough wealth for them to rebuild HP Academy better than it was before. With Gem, Ana next discovers an enormous octopus named Romeo whom she thinks can help them fight against the LI.

After they finish repairs, Ana directs the Nautilus back toward Lincoln Base. Dev and the Aronnax attack, but Romeo takes hold of the Aronnax. Ana and Gem leave the Nautilus to go rescue their friends at the base. After they rescue the hostages, they run after the Varuna, where the LI students have taken all of the alt-tech they can fit. There Ana faces her brother, who blames HP for the deaths of their parents and for denying him the Nautilus, which he believes to be his inheritance. Ana ultimately captures Dev, who underestimated her abilities. In the aftermath of all this tragedy, Hewett recovers and tells Ana how proud he is of her. Ana gives her fellow HP students the opportunity to leave HP Academy, but they all elect to stay to rebuild. Finally, Ana visits Dev in his cell, taking him to see the Nautilus so he can truly appreciate the future he had given up with his misguided and horrible actions. They use the Nautilus to visit the underground garden where the ashes of Nemo and their parents are scattered, and Ana says goodbye to her mother and father.