A 4WD, which tried to cross flooded Audley Weir at the height of Sunday's deluge, managed to reverse to safety.
"They made it out," Sutherland Shire SES said in a Facebook post update.
"We have just received footage proving that the vehicle managed to reverse out.
"This driver was incredibly lucky, if the vehicle did go any further it would have been pushed off the road by the force of the water and the occupants would have likely not survived.
"The NSW SES has completed over 250 Flood / Swift Water Rescues due to the rainfall over the weekend, the vast majority for people like this who drove into floodwater."
Sutherland Shire SES is appealing for public assistance to find out whether a motorist who drove across Audley Weir causeway at the height of Sunday's deluge is safe.
A camera at the site captured the vehicle in two metre deep water at 5.38pm.
"Okay, so we need your help please!," the SES said in a Facebook post.
"On Sunday afternoon a 4WD was spotted entering a flooded Audley Weir.
"We have exhausted every avenue to make sure the person in this photo is OK.
"We have no intention of trying to get whoever this is in trouble, we just want to know that they are OK and got out alive.
"If this is you, or you know who this is please get in touch to let us know.
"The water was 2m deep per the flood gauge when this, and other images where taken.
"For everyone else, PLEASE DON'T DRIVE THROUGH FLOODWATER."