Halton Regional Police said they responded to a call around 10:30 a.m. from someone who said there were several people in danger in the water at Coronation Park.
The Marine unit attended and rescued a 10-year-old boy from the water. According to police, he was not hurt, but was taken to the hospital as a precaution.
Paramedics and firefighters also attended and helped remove a young woman from the water near the shore.
Police said Monday night that despite life-saving efforts by first responders and at the hospital, the young woman died.
The boy and woman were not related, but were at the park together, police said. They said they would not provide further details out of respect for the families.
Halton police did not say what the two were doing in the water when they ended up in danger.
Detectives with the Bureau of Criminal Investigation are investigating the fatal incident.
