For 15 years the mermaid sat, beguiling and mysterious, along a desolate shore of Lake Michigan on Chicago's South Side. "When I first came across her, the water was high and her fins were in the water," says area resident Karl Pine, 39, of the voluptuous, reclining, 7-ft. limestone figure. "It was really striking, and you think, 'Gee, where did this come from?' "

When workers at Burnham Park finally discovered the sculpture last November, the city started wondering too. Then Malinda Garcia, 30, came clean. In 1986, she revealed, she had spent almost two weeks posing in her bikini as her father, Roman Villarreal, and several of his artist friends chiseled the mermaid into the stone. "My dad said, 'You'll be immortal,' " recalls Garcia, a married data analyst for UnitedHealthcare with three kids. "And I was like, 'All right, cool!' "

Because he lacked the proper permits for his public art, Villarreal, 51, a former steel-mill worker, chose a seldom-visited section of the lakefront and snuck into the park in the early morning hours. "Everyone was excited because we were doing something so different," remembers the artist, who lives nearby with wife Maria, 47, an art teacher. And though he never realized his plan to create a new sculpture each summer in that same location, Villarreal admits he's pleased that park officials now plan to preserve his mysterious stone lady. "The mermaid came out of a whim," he says, "and years later it surfaces to something we never expected."