It's A Bikini World (1967) - (Movie Clip) Spread It On Thick
The song credit is "Wilkins-Hurley-Cates" and the band (frat-rockers "The Gentrys") had broken up by the time the movie was released, but it's snappy enough, with Tommy Kirk and Bob "Boris" Pickett advancing the beach-movie plot, in It's A Bikini World, 1967.