Searching for a movie early 70s

It started with a scene in bath, soon after that girls were take on a yacht or boat, kidnapped. Then as i remember the girls were with pirates or so, also a female pirate leader was there. Later on the girls were working as waitresses. The movie must be 1970 to 1977, i have seen the movie here in western europe even in the cinema back then (!), but i never found it online.