The female in the group found herself ''stuck'' beyond the waves and unable to swim back in.
Miss Thirlwell said she and her mother were concerned as it was not considered a safe swimming beach.
The tourists appeared to be reasonably far out and were in there ''for quite a while''.
One of the men in the group, understood to be the distressed woman's husband, came out of the water when Miss Thirlwell approached him.
''I just initially spoke to her husband. He said she was a strong swimmer.''
Then, the other male in the group came out of the water.
''[He] said 'she's stuck out there'.''
Miss Thirlwell ran into the surf and swam with the woman's husband to try to rescue her.
Mrs Hughes said the woman swallowed quite a bit of water.
''At one point she was under.''
When Miss Thirlwell and the woman's husband dragged the distressed woman out of the water, she could barely walk.
The rescue was over pretty quickly, Miss Thirlwell said.
''She was hysterical. She was in shock,'' Mrs Hughes said.
Emergency services were called about 11.20am.
A police spokeswoman said when police arrived the woman was already out of the water and had been walked to the ambulance by Fire and Emergency New Zealand personnel.
A St John spokesman said the woman sustained minor injuries and was assessed and treated at the scene.
Miss Thirlwell said the beach was ''pretty deceiving''.
''It looks significantly calmer [than other beaches].''
Mrs Hughes believed there should be a sign warning visitors of the dangers at the beach.
Locals knew the risks but freedom campers often did not realise it was not particularly safe for swimming, she said.
