Girl drowns after NSW boating incident

A young girl who disappeared off a boat on the Hawkesbury River north of Sydney has died after being rescued by water police and flown to hospital.

Emergency services were called to the river at Brooklyn at 12.45pm on Tuesday following reports a child had gone missing from a boat.

Water police located the three-year-old in the river a short time later and commenced CPR, a spokeswoman said.

The toddler was taken to a nearby boat ramp where NSW Ambulance paramedics took over her treatment.

The three-year-old was then airlifted to the Children's Hospital at Westmead in a critical condition but was pronounced dead after arrival.

Paramedics described the scene as chaotic and emotional.

"It's a gut-wrenching incident," NSW Ambulance Superintendent Jordan Emery told the Seven Network.

"These paramedics are mothers and fathers themselves, they have siblings, nephews, nieces that same age and we're not immune form that incredible suffering that accompanies jobs like this."

Police are investigating the incident.