Harris County sheriff's deputies believe the child fell into the water around midnight in the 7500 block of Coral Lake Drive, near Montego Breeze Lane in the Cypress area.
Deputies said adults performed CPR on the child, who is now in critical condition in the hospital.
Sheriff Ed Gonzalez added that the child has autism spectrum disorder.
Although the exact circumstances in this case are unknown, it's a reminder that parents are urged to learn CPR and keep a close eye on children around water.