Jacob Tremblay as Luca Paguro, a 13-year-old sea monster curious of the world above the sea.[7] Jack Dylan Grazer as Alberto Scorfano, a teenage sea monster enthusiastic for the human world.[7] Emma Berman as Giulia, an Italian girl who befriends Luca and Alberto.[7] Maya Rudolph as Daniela, Luca's mother[7] Marco Barricelli as Massimo, Giulia's father[7] Jim Gaffigan as Lorenzo, Luca's father[7]