Zany foursome Errol (Christopher de Leon), Herman (Jay Ilagan), Tacio (Johhny Delgado), and Peewee (Edgar Mortiz) merely geared up for a short underwater dive towards Hundred Islands when a series of miscalculations cause them to resurface on the shores of Mexico. As they try to reorient themselves for their homebound dive, a dying man entrusts them with a battered sombrero which happens to be coveted by loony adventurer Lastiko (Jaime Fabregas) and his formidable henchman Alagua (Larry Lawrence). The sombrero turns out to bear a map leading to an enormous fortune that is by rights owned jointly by the Philippines and Mexico, but Lastiko wants to get hold of the map in order to horde the treasure for his insanely villainous motives. With the help of Macy (Gigette Reyes) and special agent Cayugyug (Nora Aunor), the four race after Lastiko in pursuit of the treasure–but will their combined forces outwit a reckless but determined madman?