A man and teenager have been taken to hospital after a whale reportedly hit their boat off Narooma on Sunday, June 6.
A witness said they were lucky to make it back to shore.
Francois Van Zyl of Underwater Safaris was getting ready to launch his boat for a dive tour when he saw paramedics at Apex Park 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 happened 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 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 male teenager 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 manoeuver boats at the boat ramp and assisted paramedics to carry a patient to the ambulance.
"Narooma paramedic staff were unbelievable and did everything they could," he said.
After helping at the scene, Mr Van Zyl continued his tour to Montague Island.
"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 12-16 metres long and weigh around 25-30 tonnes.