A man clung to a tree in a river north of Bega overnight before he was rescued early on Tuesday.
NSW State Emergency Service crews found the man in floodwaters just before 4am.
It's understood the man had been clinging to a tree in the Brogo River since 6pm on Monday.
Three SES members from Queanbeyan-Palerang supported by four Bega Valley members rescued the man, who was then taken to South East Regional Hospital in Bega.
Several parts of the South Coast experienced flooding on Monday after heavy rain.
On Tuesday NSW SES Bega Valley units said significant volumes of water and strong flows were still being experienced in some locations.
It advised conditions in the Bega, Brogo, Bemboka and Towamba rivers and all surrounding creeks and waterways were dangerous.
The SES said it was not safe for people to drive, ride, walk or play in the floodwaters.
Rain and flooding has caused some road closures.