Two women have been charged with the attempted murder and kidnapping of a 19-year-old Campbelltown woman after allegedly forcing her into the boot of a car and throwing her 30 metres from Windsor bridge into the Hawkesbury River.

The 19-year-old woman, who was allegedly held against her will on Saturday night, managed to swim to the riverbank and seek help on Sunday, September 22, at 5:00am.

She was taken to Nepean Hospital for treatment, and New South Wales Police are inquiring about the possible involvement of two men.

A 17-year-old woman and a 19-year-old woman were arrested and charged with attempted murder, aggravated kidnapping, wounding a person with intent to cause grievous bodily harm, and robbery with wounding.

Police officers from the Hawkesbury Local Area Command seized a Holden Commodore in Whalan.

They will allege that the victim was transported from Campbelltown to Windsor in the car's boot.

The charged 19-year-old woman was arrested yesterday and was refused bail to appear in Penrith Local Court.

She was further refused bail and is expected to appear at the same court in November.

The 17-year-old girl was also refused bail and will appear at a Children's Court tomorrow.