A man and teenager have been taken to hospital after a whale reportedly hit their boat off the NSW South Coast.
A witness said they were lucky to make it back to shore after being swamped on Sunday, June 6.
Francois Van Zyl of Underwater Safaris in Narooma, about 280 kilometres south of Sydney, was getting ready to launch his boat for a dive tour when he saw paramedics at a boat ramp.
"Being a small town, I offered my assistance when I saw two gentlemen were being treated on the jetty," he said.
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NSW Maritime was investigating the incident which occurred at about 7.50am.
"A whale breached and landed on two men travelling to go fishing in a 4.9 metre cabin runabout, about 500 metres off Narooma," a NSW Maritime spokesperson said.
"The younger of the men suffered critical injuries and remains in hospital.
"It is unknown whether they were wearing lifejackets at the time of the incident."
Mr Van Zyl was told a breaching whale caused damage to their boat.
He said the boat was badly damaged and that it was fortunate to have made it back to shore.
"The console area was separated from the hull," he said.
"It wasn't a very large boat, I am surprised it hadn't submerged."
NSW Ambulance said the teenage boy and 40-year-old man suffered neck and head injuries and were taken to Moruya District Hospital.
"It was very unfortunate for them to endure that stressful situation," Mr Van Zyl said.
"We live on a nature coast, where you expect to see nature and interact with it. They were at the right place at the wrong time."
Mr Van Zyl said he helped to manoeuvre boats at the Apex Park boat ramp and assisted paramedics to carry a patient to the ambulance.
Locals said they thought the injured pair had been fishing.
"Narooma paramedic staff were unbelievable and did everything they could," Mr Van Zyl said
After helping at the scene, Mr Van Zyl continued his tour to Montague Island, about 9 kilometres away.
"It was a beautiful day, with flat and sunny conditions," he said.
"We saw lots of whales, they were everywhere.
"You would be looking at one whale and then four would pop up behind you."
June marks the beginning of humpback whales' migration from Antarctica to Queensland waters.
"They're expected to get to the Great Barrier Reef by August to give birth - it's a bit of a rush for them to get there," Mr Van Zyl said.
"They are expected in this area until July."
Adult humpback whales can be 12 to 16 metres long and weigh 25 to 30 tonnes.