The $7 million center on Browns Mills Road in Lithonia has been under lock and key since it was completed in April.
Adults and children eager for wet 'n' wild fun in the face of recent 90-plus degree weather, have been frustrated by the delay.
The center was originally scheduled to open in July but county spokeswoman Kristie Swink said it was delayed by "scheduling conflicts."
Commissioner Lee May, in whose district the water park sits, said his constituents are excited about the park finally opening.
"They've been kind of upset that it has taken so long, but they'll be more than happy to see it open for kids, youth and adults," he said.
The 10 a.m. grand opening ceremony will feature a ribbon cutting, prizes, facing painting free food and balloons.
The 84,776-square-foot center features 330,000 gallons of water slushing around in two pools, a 25-foot, three-lane swimming pool and a wading pool, a lazy river for tubing, and two soaring water slides.
There are also interactive water features such as huge water buckets that will pour water on park goers. Swink said the park can hold up to 900 people.
The DeKalb Aquatic Center will join 12 pools and 16 lakes managed by DeKalb Parks and Recreation Department.
The park will stay open until the end of September and reopen in May 2009 for the summer.
Park hours will be Mondays to Saturdays from 9 a.m. to 8:30 p.m., and Sundays from 1 p.m. to 7 p.m.
Children up to age 4 will pay $2. Youth 5 to 17 will pay $3. People 18 years and older will pay $5.
The DeKalb Aquatic Center is next door to the Browns Mill Recreation Center on Browns Mill Road. For more information, call 404-371-2631.