A SEARCH is under way for a Canadian man who is missing, feared drowned, after a late-night swim on the NSW south coast.

Police said the 31-year-old went swimming with a friend at Surf Beach, Kiama, about 12.40am today.

"The two men were in the surf for about five minutes when his friend noticed the 31-year-old was missing," a NSW Police spokeswoman said.

Emergency crews were called to the beach and an initial search, which included the rescue helicopter, was conducted in the dark.

A full search resumed this morning, involving the Kiama Surf Life Saving Club, State Emergency Service, water police and Polair.

The Canadian had been living in the Kiama area for some time, the spokeswoman added.