A man is in a critical condition after a tree branch fell on him in a "freak incident" at a dam southwest of Sydney.
The 65-year-old suffered a head injury and went into cardiac arrest after being hit by the branch at Cataract Dam about 1.45pm on Sunday.
He was treated by paramedics and airlifted to Liverpool Hospital.
NSW Ambulance Inspector Norman Rees praised bystanders for helping the stricken man until paramedics could begin treatment.
"It was a very chaotic scene with a number of families enjoying picnics in the sunshine when the freak incident happened," Insp Rees said in a statement.
"Accidents like this are absolutely tragic, especially during the holiday season when we are out and about spending time with our loved ones.
"Bystanders did an incredible job to help the man until emergency services arrived."