What appeared to be a harmless, childish game turned out to be very dangerous for a boy from Spanaway. On Thursday, the boy was playing outside his house with his little sister when he suddenly fell into a pool, almost drowning.

Pierce County Sheriff’s Department representative Detective Ed Troyer said deputies and fire medics responded to a report of drowning around 2:35 p.m., the Seattle Times reports.

According to the police, the boy, 4, climbed through a fence hole in the 15600 block of 15th Avenue Court East and fell into the pool, which was located in the backyard of the home. He was lucky to have his 5-year-old sister there playing with him, who saw what happened and called her parents for help.

The father came and immediately dove into the pool, which was full of rainwater looking almost green and slime. Although he had no visibility, he succeeded to find the boy on the bottom of the pool. He pulled him out the pool and started CPR on him.

When the rescue team came, the boy was immediately rushed to Mary Bridge Children’s Hospital in Tacoma. Unfortunately, he was listed in critical condition on Thursday night, Troyer said.