Set in a seaside town on the Italian Riviera, a young boy experiences an unforgettable summer. Luca shares his amazing adventures with his newfound friend Alberto, but their fun is threatened by a deeply held secret: they're sea monsters from another world just below the water's surface.

The monster family embarks on a vacation on a luxury monster cruise ship so Drac can take a summer vacation from providing everyone else's vacation at the hotel. It's smooth sailing for Drac's Pack as the monsters indulge in all of the shipboard fun the cruise has to offer. But the dream vacation turns into a nightmare when Mavis realizes Drac has fallen for the mysterious captain of the ship, Ericka, who hides a dangerous secret that could destroy...