The teen, James Charles Eader, went by Jimmy. Police say he had severe autism and seizures and was non-verbal.
Family members say they had looked in the pool several times for the teen, but the pool is very murky and the bottom of it couldn't be seen.
He was last seen around 2 p.m. Thursday in the 100 block of Bluff Heights; a rural area of Parker County about 12 miles northeast of Weatherford.
The sheriff's office and the Department of Public Safety deployed officers, K-9 officers, and helicopters in an effort to find him.