Fabian shaved off his chest hair in order to give his torso a smooth look for his many "beefcake" scenes.
Tab Hunter darkened his hair and Peter Brown lightened his hair in order to better match the athletes who did the actual surfing for them in the movie.
The first feature film directed by TV-veteran Don Taylor. When his mother died during filming, Columbia brought in Phil Karlson to direct a few scenes in Taylor's absence. According to Tab Hunter's autobiography, Karlson directed the scene in which Hunter assures his future mother-in-law that he's not a beach bum but rather a hard-working citizen.
Those shots of Fabian, Peter Brown, and Tab Hunter - photographed from mid-chest up - riding their surfboards were actually shot in California inside Columbia Studios. The actors balanced on Radio Flyer wagons in front of a rear-projection screen showing ocean waves. Assistants then sprayed them with water while maneuvering the wagons to give the desired effect.