The incident happened around 7:15 p.m. Sunday, July 7, in Deer Park.
The child, a 2-year-old boy, was pulled from the pool, and first responders began CPR upon arriving on the scene.
The boy was transported by ambulance to Good Samaritan University Hospital in West Islip and later moved to Stony Brook University Hospital in stable condition.
Anyone with information on the incident is asked to contact First Squad detectives at 631-854-8152.
Click here to follow Daily Voice Cold Spring Harbor and receive free news updates.