Land of the Lost (1991)

The Porters, Stink, Tasha and Christa spend the day on the beach with Namaki. But one by one, the Porters vanish without a trace as hypnotic music plays. Namaki, Tasha and Stink search for them and find that the Porters are being held by a shape-shifting siren (imprisoned by a serpent) and she wants them to become her family.