The Ghost in the Invisible Bikini

Ghost in the Invisible Bikini according to the film itself and all advertising material is the seventh and last of the American International Pictures AIP beach party films and was released in 1966. The entire film takes place in and around a haunted house with no beach in sight, with the teenage gang instead cavorting in and around it and the adjacent swimming pool.

The ghost of recently dead Mr. Hiram Stokley Boris Karloff finds that he hashours to perform one good deed to get into Heaven. He enlists the help of his long dead girlfriend, Cecily, to stop his lawyer, Reginald Ripper Basil Rathbone, and a henchman from claiming the estate for themselves. The real heirs, Chuck, Lili, Hirams cousin Myrtle, and her son bring their beach party friends to the mansion for a pool party while Reginald Ripper also employs his daughter Sinistra, and J. Sinister Hulks slowwitted associates Chicken Feather and Yolanda to help them terrorize the teens, while dopey biker Eric Von Zipper and his Malibu Rat Pack bikers also get involved in pursuing Yolanda for a share of the Stokley estate.The project originated as Pajama Party in a Haunted House being first announced by AIP in January 1965. It was part of a line up of Beach Partylinked projects from the studio, the others including Beach Blanket Bingo, How to Stuff a Wild Bikini, Ski Party, Sergeant Deadhead, The Chase Jet Set Party, and a Beach Party TV series. The last three of those announced were never made. ........

Source: Wikipedia