A surfer has been injured while being towed onto a massive wave off the Margaret River coast.

Gold Coast man Justin Holland was surfing at the Cow Bombie break, off Cowaramup Bay, this morning in a huge swell when he was overrun by the wave.

The 35-year-old and his friend, Gold Coast big wave surfer Jamie Mitchell, were making a documentary at the time.

Mitchell said he had already towed Holland onto three or four medium-sized waves.

"Then a really big one came through, probably the biggest one all day," he said.

"And he was a little bit too far behind the peak and straightened out and the wave literally broke right on the tail of his board and just really detonated him really hard.

"He had to take one more on the head and then I went in and grabbed him and he was screaming his leg, his leg."

Sorry, this video has expired A man is injured surfing a big wave off the coast near Margaret River ( Audience submitted )

Mitchell pulled him onto the jet ski's rescue sled and immobilised his leg.

The pair had hired another jet ski driver Keighley Bremner, who also came to the rescue.

"I came in on a ski in front of him and then we just carried him up," Mr Bremner said.

They took Holland back to shore at North Point, inside Cowaramup Bay, where an ambulance took him to Margaret River Hospital.

Mitchell said it looked like the father of two had snapped his femur and would be moved to Bunbury Hospital for surgery.

"It's going to be a long recovery, but he's a strong guy so he'll be fine," he said.

Big wave surfers search out perfect break

Sorry, this video has expired Surf swells in Western Australia ( Roxanne Taylor )

The surf has been huge in the Margaret River area since Friday, when a big swell generated by a low pressure system in the Indian Ocean a week ago hit the coast.

Big wave hunters from around the country have flown into the region and have been taking on five-metre waves at the Cow Bombie break and other big wave spots.

The swell dropped just below five metres today, although there are reports the waves are still as big as yesterday and in some cases, bigger.

The swell is expected to ease significantly tomorrow.