Lucas

The film opens in Italy, where two fishermen are out on their boat at night. Their record player is suddenly pulled underwater by a mysterious sea monster.

Under the sea, we meet Luca Paguro, a curious young sea monster living with his parents and Grandma. Despite warnings to stay away from the surface, Luca is drawn to it, encouraged by his Grandma's gentle nudging.

Luca discovers the record player from the fishermen and hides in a cave upon seeing a diver. However, he soon learns that the diver is another sea monster, Alberto, who transforms into a human and encourages Luca to join him on land.

Luca follows Alberto to his secret hideout, filled with trinkets from the human world. They bond over a poster of a Vespa, which ignites their dream of owning one together.

Luca and Alberto spend time constructing a makeshift Vespa while dodging warnings from Luca's parents. They face setbacks, but Alberto's encouragement drives Luca to overcome his fears.

When Luca's parents decide to send him away for the summer, he and Alberto hatch a plan to travel to the nearby town of Portorosso. They seek to win the local triathlon to earn the money for their own Vespa.

In Portorosso, the boys encounter a girl named Giulia who shares their disdain for the local bully, Ercole. They convince her to form a team for the upcoming race in hopes of winning a prize.

Luca, Alberto, and Giulia prepare for the triathlon, training for the swimming, eating pasta, and biking portions. They face challenges, especially from Ercole, who tries to undermine their confidence.

Luca connects with Giulia, sharing feelings of being an outsider. However, Alberto's jealousy grows as he feels left out, straining their friendship just before the race.

On the day of the Portorosso Cup, Luca and Giulia participate, while Alberto remains hurt and isolated. The race becomes chaotic, revealing Luca and Alberto’s sea monster forms to the townspeople.

During the final parts of the race, Alberto is attacked and reveals his sea monster identity to the crowd. Luca soon follows suit, showing his true self to save Alberto, shifting their dynamic forever.

Despite initial fear and anger, townsfolk rally behind Luca and Alberto as Massimo, Giulia’s father, defends them. Their fellow racers turn against Ercole, marking a significant change in community sentiment.

The boys are celebrated as the winners of the Cup, and their families embrace them with pride. The acceptance of their sea monster forms by the community marks a turning point, leading to widespread celebration.

As Giulia prepares to leave for Genova, Luca's parents decide he can accompany her. Alberto selflessly sells the Vespa to fund Luca's train ticket, leading them onward towards new adventures.

The story concludes with Luca and Giulia having fun in Genova, while keeping in touch with Alberto and his new life. Their friendship remains strong, symbolizing acceptance and adventure.