Catalina Caper (1966)

Starring Tommy Kirk, Del Moore, Peter Duryea, Robert Donner, Ulla Stromstedt
Directed by Lee Sholem
(actor & director credits courtesy IMDB.com)

A pair of teens vacation in Catalina, and stumble across a plot to sell a valuable stolen scroll.

Pretty much a clone of the "Beach Party" films of American International Pictures, borrowing Tommy Kirk who appeared in some of those to star, but it's a pale imitation, most notable for a performance by rock n'roller Little Richard, and the casting of future TV star Lyle Waggoner in a small role.  It's not terrible, even though the musical numbers are forgettable, and most of the comedy falls flat, although I had to snicker when the adult characters try to dance.