Seven adults and a baby were trapped on a boat that smashed into rocks at the South Coast.

Westpac Life Saver Helicopter CEO Stephen Leahy said the boat had hit rocks at Batehaven on Monday afternoon, just south of Batemans Bay, where the sea was very rough.

A rescue crewman had been winched onto the boat and confirmed that everyone on board was unharmed.

A marine rescue boat was close by but the conditions at sea were too bad to use it, so smaller surf lifesaving rescue boats were used.

"This is quite dangerous indeed, the boat is being pounded up on rocks, it will be a difficult operation," he said before the people were rescued.

Mr Leahy said he did not know at this stage how big the boat was, whether the people on board were men or women or where they were from