A search is under way for a swimmer missing in the Hawkesbury River north of Sydney.
Police say a group of friends were swimming in the river, west of the Windsor Bridge, just before 6pm (AEDT) on Wednesday when a man got into difficulty.
Emergency services were called to the scene after the man, believed to be 22, failed to surface.
A police helicopter and PolAir are searching the area.
Police divers are en route.