[5] Ana Dakkar is a 15-year-old student at Harding-Pencroft Academy, a fictional five-year boarding high school for marine sciences, situated on a remote bluff on the southern California coast.

On a Friday morning just before the end of Ana's freshman year, she goes for a swim near campus with her older brother Dev, a 17-year-old senior, who gives her their mother's pearl necklace as an early present for her fifteenth birthday.

Shortly after leaving the campus, Ana and her classmates see torpedoes fired from a submarine at the base of the bluff on which their school sits, collapsing the buildings into the ocean.

Dr. Hewett, after launching drones to survey the wreckage, orders the freshmen back onto the bus, then onto the Varuna and out to sea, telling them that this is the work of a rival school, Land Institute, and that it is better for their own safety if the world believes them dead as well.

The abduction is foiled with the aid of a friendly bottlenose dolphin Ana named Socrates, who knocks her would-be abductor, Caleb South, out of the water.

When interrogated, Caleb proudly admits that he and his classmates destroyed Harding-Pencroft and says that they were protecting the legacy of an outlaw and selfishly hoarding technology that could greatly benefit the world.

Hewett has him thrown overboard in his flotation vest and wet suit (plus water wings, which are a form of hazing for inept students at Harding-Pencroft) to join his classmates who have been set adrift in a pontoon with their hands bound.

Luca and Ophelia introduce the students to the Nautilus, which, save for some relatively minor internal water damage, is almost intact, after sitting dormant at the bottom of a nearby lagoon for approximately 150 years after Captain Nemo died in the command chair.

Ana and her classmates' exploration of the Nautilus is suddenly interrupted by the discovery that the Land Institute seniors who attacked their school have followed them to Lincoln Island in their submarine the Aronnax, and a battle ensues.

During the battle, Ana and the others discover to their horror that her brother Dev, thought dead, has been collaborating with Land Institute, and is commanding the Aronnax, from which he had broadcast the warning to evacuate after Harding-Pencroft Academy's defenses had been hacked and brought down.

Ana discovers that Dev has hidden a tracking device in the necklace he gave her and immediately destroys it, then uses the Nautilus's advanced propulsion systems to flee.

[3] Shelf Awareness also provided a starred review, highlighting how the novel's, "more serious discussions, along with the inclusion of marine biology and AI concepts, are balanced by unexpected twists, heart-pounding action and vivid language".