Choonhwa Lee, 43, was booked into Sacramento County Jail on suspicion of endangering the life of a child.
The little boy, who was administered cardio pulmonary resuscitation by a neighbor, was initially listed in critical condition. However, police said Thursday that the boy had recovered enough to be released from the hospital.
Police gave this account of what happened at the apartment house pool in the 600 block of Garden Highway near Northgate Boulevard:
A resident of the complex was outside with a view of the pool and could see the two-year-old face down in water that was about three feet deep.
The little boy's four-year-old brother was either standing on the steps leading into the pool or on the pool edge holding onto his younger sibling's hand.
The good Samaritan hurried to the pool and pulled the child's limp body from the water. She administered CPR and then took the child to the front desk office where 911 was called.
A police activity log said Lee was "a substantial distance from her children during the incident."
Police declined to give the woman's name who delivered CPR because she is a witness.
"What a great job by this person," said police spokesman Sgt. Andrew Pettit.