With his best friend Luca away at school, Alberto is enjoying his new life in Portorosso working alongside Massimo – the imposing, tattooed, one-armed fisherman of few words – who's quite possibly the coolest human in the entire world as far as Alberto is concerned. He wants more than anything to impress his mentor, but it's easier said than done.

Luca and his best friend Alberto experience an unforgettable summer on the Italian Riviera. But all the fun is threatened by a deeply-held secret: they are sea monsters from another world just below the water’s surface.