Powerful surf across the NSW coast has caused "chaos" for lifesavers as a tropical cyclone in the South Pacific Ocean forms dangerous conditions across the coastline.
Dangerous surf conditions battered the coast on Saturday with hazardous conditions forecast for Sunday as Tropical Cyclone Gita - which damaged parts of southern Fiji - moves from the southwest of New Caledonia towards the Tasman Sea, the Bureau of Meteorology says.
While the cyclone isn't expected to reach NSW, it will cause dangerous surf conditions with swimmers, surfers and rock fishers urged to stay out of the water.
Surf Lifesaving NSW said the powerful surf caused chaos on the coast with several swimmers getting into difficulty as a result of the challenging conditions on Saturday.
"There are serious concerns for a 22-year-old swimmer who went missing after getting caught in a rip at Valla Beach on the state's north coast," Surf Lifesaving NSW said in a statement on Saturday.
A 15-year-old was pulled from the water by lifesavers at Kiama beach on the NSW south coast and is recovering in hospital.
Two swimmers were rescued by surfers at Turimetta Beach in Sydney's northern beaches, while a surfer was taken to hospital after swallowing water at South Narrabeen, Surf Lifesaving NSW said.
A mass rescue was carried out at Avoca beach on the Central Coast by lifesavers who used a jet ski and an inflatable rescue boat to pull six people from a rip current.
Surf Lifesaving NSW manager Matt du Plessis urged beachgoers to not get complacent as swells are expected to peak at more than three metres on Sunday.
"Please take note of the safety warnings and if you have any doubt whatsoever about your ability to handle the water it's better not to go in," Mr du Plessis said in a statement on Saturday.
The waves on Sunday won't appear high and dangerous, but the length of time between consecutive waves will be fairly long, increasing the power of each wave, bureau duty forecaster Rob Taggart said.
"Because the water appears relatively flat it doesn't look like it will be dangerous but it carries a lot of energy and has the potential to sweep people away," Mr Taggart told AAP on Saturday.
The bureau has issued a hazardous surf warning for the entire NSW coastline for Sunday.
A big swell is set to come in on Monday and Tuesday as Gita moves into the Tasman Sea.
"Visibly, you will be able to see (the large swell) and the wave heights will pick up," Mr Taggart said.
Australian Associated Press