Koscina was born to parents from Split and Trogir ("Košćina" in čakavian Croatian means "a great bone"; Košćina was a family name of the owner of the first greater shipyard in Split, established 1831). Her publicity agents invented that she was born "Sylva Koskinon" of a Greek father and a Polish mother. She may be best-remembered for her role as Iole, the bride of Hercules (Steve Reeves) in Hercules (1958) and Hercules Unchained (1960). She also played Paul Newman's romantic interest in The Secret War of Harry Frigg (1968).