It's shortly after noon, and something evil's lurking in the pool.

Under the sunlight, you see a sight that almost stops your heart — 100 day campers zombie-walking around Frances Meadows Aquatic and Community Center.

"We didn't know what they were doing. I thought they were getting a picture. It was awesome," said Mackenzie Satterfield, 14, a rising ninth-grader at West Hall High School.

The surprise "Thriller" flash mob performance was done by kids in the Discovery Summer Day Camp hosted by Gainesville City Parks & Recreation as part of a nationwide movement to "Rock Your Park."

"We don't think there's been a flash mob in Gainesville, and we wanted to be the first," said Julie Butler Colombini, marketing and communications manager for the department. "We are actually calling this a splash flash mob, since it is at the Splash Zone."

When lifeguards blew their whistles for the hourly safety break, all swimmers climbed out of the water for a 10-minute bathroom and snack break.

The day campers, ranging in age from 6 to 12, were all dressed in their blue camp T-shirts. They walked into the Splash Zone area, put their bags down, and lined up in front of unsuspecting aquatic center patrons. Two groups of younger campers flanked a center group of older kids.

The moment the familiar strains of Michael Jackson's hit came over the loudspeaker, the kids broke out into their dance. The splash mob culminated with the 9- to 12-year-old campers zombie-walking into the pool in true "Thriller" fashion.

"It was pretty exciting, but I felt kind of shy when it started," said Tyler Lee, 10, a rising fifth-grader at Enota Multiple Intelligences Academy.

Both Alaysha Turner, 12, and Adrianna Flores, 10, learned "Thriller" previously, and were recruited to help Jarrad Howard, the lead day camp counselor, choreograph the dance with the younger campers.

"Ages 6, 7 and 8 did a more modified version to frame the older kids, who did the entire dance," Howard said. "None of them had ever been a part of a flash mob."

Howard, who has taught dance lessons as part of the Discovery camp for two years, learned "Thriller" from watching a YouTube video. Howard had dance lessons for each age group of campers, and Colombini said the kids spent several weeks practicing for the performance.

The hardest part of teaching the dance to 100 campers?

Teaching the dance to 100 campers, he said, since the key to the dance becoming a flash mob was keeping it a secret.

"It was hard containing their excitement," Howard said. "They all wanted to talk about this."