Bishan Rajapakse, a 38-year-old doctor from Bondi, was knocked unconscious for 10 seconds when he was struck by a whale, thought to be a southern right, while surfing at Bondi Beach on Sunday morning.

The surfer was taken to St Vincent's Hospital and is in a satisfactory condition. "It was a near drowning," said Gordian Fulde, director of the emergency department at St Vincent's. "But he has no broken bones. He will probably go home tomorrow."

Rajapakse, a Sri-Lankan born New Zealander, said he had been surfing at the southern end of the beach for about an hour on Sunday when his friend Chris signalled for him to paddle over.

“When I got to him I saw there was this dark, black shadow and it was just massive. The whale was moving in like slow motion. It was beautiful and it breached and we could see the barnacles and it was slowly going up and down and turning and it actually made a noise. It was amazing."

He said the last thing he remembered was saying, “Hey, how's it going?” to the whale which was less then a metre from him.

Speaking from his hospital bed, Dr Rajapakse said he had no injuries apart from a slight headache.

Paul Martin, a lifeguard at Bondi Icebergs, said the whale "came in 75-100 metres off the rocks" on the southern end of Bondi beach. "The whale ran into a group of surfers and decided it was going to play football with one of them."

A lifeguard at Bondi Rescue, Anthony Carroll, said the victim was about half a metre from the tail of the whale.

"A local surfer, Tony Spanos, held him up while he was unconscious for 15 seconds face down," Mr Carroll said. "His board had been smashed in pretty badly. It looked like he was thrown about three metres above the water.

"The tail of a whale is the strongest muscle on any animal in the world. Some humpback whales get up to 80 tonnes. It's an extreme no-no to go in the vicinity of a whale."

Mr Spanos said the whale was "cruising around for 15 minutes. He was quite inquisitive. He was just watching us. The whale looked mid age, with lots of barnacles on its back. It was about 10 metres long."

The victim "got really heavily smashed and went straight under," said Mr Spanos. "I dived down and grabbed him. There was a guy out there on a big mal. I called him over, we lifted him on and we started paddling back to shore."

Victim 'just kept staring at the whale’s head'

Mark Greig, son of the late cricket legend Tony Greig, had warned the injured surfer - believed to be of Sri Lankan background - to move away from the whale seconds before the animal’s tail smashed him in the head.

Mr Greig and Jeremy Piggin had been surfing a small break in the middle of the bay when the whale appeared about 10am and swam among the surfers.

Mr Piggin said about 15 people - 10 board riders, including two young women, a couple of body boarders and a couple of body surfers - watched as the animal drew near and looked at them. ‘‘He just kept swimming around and looking at us. It didn’t want to go away. It was as if he wanted to play with us,’’ Mr Piggin said.

‘‘It was huge. Being that close made it just surreal. At one point Mark dove under the water to get a close-up look and saw the whale’s flippers nearly dragging along the sand. It was that shallow.’’

Mr Piggin said as the animal started to move around more, some of the surfers moved away but one stayed still. ‘‘He just kept staring at the whale’s head. At one point Mark called out to not get so close but he didn’t seem to have any idea about that tail and it came out of the water and just whacked him.’’

Mr Piggin said the surfer was knocked out and sank. ‘‘The girls were screaming and some of the other guys dove down and got him. His eyes were all rolled back and his arms were limp. It was obvious he was unconscious,’’ Mr Piggin said.

‘‘Mark started signalling to the lifeguards and they came out and got him.’’

The whale remained off Bondi for two hours. Shortly after 12.20pm, it moved around Ben Buckler Point and headed north under the escort of a police boat and three jet skis.

'It was as big as a bus, easily 40 foot long'

"Guys just went everywhere," said Lachlan Harris, a businessman. "It was as big as a bus, easily 40 foot long and it just sent the surfers flying like skittles."

Surfers near the whale started sending distress signals. When the lifeguards carried the man to the sand, they put him into a neck brace. An ambulance arrived about 20 minutes later.

The beach was packed with strollers, joggers, skateboards and coffee drinkers taking in the perfect clear-sky morning.

Mr Harris, a member of Kevin Rudd's staff during his first term as prime minister, had been taking his regular Sunday walk along the clifftop from Bondi and Bronte when he noticed the whale. "The whole beach just stopped to watch. It was unreal. It just swam among this group of 15 guys on boards and a couple of swimmers in the middle of the bay and it looked like he was playing with him. We all just stood there riveted.

"And then, whoosh, up comes the tail, and up go the guys," he said.

Mr Harris said at least 300 people at Bondi Icebergs had a ringside seat. "Looking north along the sand, the whale was sort of behind them and they could see the whole thing. Everybody had their mobile phone cameras going off.

"It was just amazing. I mean there were people swimming laps of the beach and the whale was even inside them. It was that close to the beach."