Night of the Seagulls

"Night of the Seagulls", a 1975 Spanish horror film, tells the story of Dr. Henry Stein (Víctor Petit) and his wife Joan (María Kosti) who move into a primitive coastal town plagued by an ancient evil: every seven years, undead Knights Templar rise from the sea to demand the sacrifice of a young maiden, with Dr. Stein and his wife attempting to save one of the maidens, Lucy (Sandra Mozarowsky).