(CapeArgus / 20-07-10)  Those pictures shows the southern right whale seconds before its massive body landed on the coach roof of the boat, flattening the steel mast and bringing down the rigging before sliding back into the water and disappearing into the distance.

"It was quite scary," said Paloma Werner, who had been out sailing with her boyfriend and business partner, Ralph Mothes, of the Cape Town Sailing Academy.

"We thought the whale was going to go under the boat and come up on the other side. We thought it would see us." But the boat had its engine turned off.

Meredith Thornton, scientist and manager of the Cape Town Mammal Research Institute at the University of Pretoria, said: "Whales don't see much by way of their eyes but by sound in the water."

Between the whale's poor eyesight and low visibility in the water, Thornton said the whale, which she believed to be young, probably did not know the boat was in its way.

The couple first saw the whale when it was about 100m away. It breached once and, before they knew it, the whale was a mere 10m from their yacht.

"There was hardly any wind, so we couldn't get out of the way," said Werner.

"We didn't have time to take any evasive action."

The yacht, a 10m training boat called Intrepid, is made of steel and did not suffer any structural damage.

"If it had been a fibreglass boat it would have been sunk, so we were lucky," said Werner.

The whale was seen pounding its tail on the surface of the water just moments before breaching.

"It looked like it was angry or something," said Joseph Mbaya, a sailor and tour guide for Yacoob Tourism.

He had stopped his boat, Ameera, just 300m short of the whale to take photographs.

Thornton said the whale had not been angry, but was probably "lob-tailing" in order to communicate with other whales.

"If a whale wanted to be aggressive it would side-swipe the boat with its tail," she said.

Two people from Botswana were on Ameera with Mbaya.

One of the tourists, who Mbaya knew only as James, captured the moment on his camera just before the whale hit the boat.

James gave a copy of the picture to Mbaya as a keepsake and the tour guide brought it to the Cape Argus.

After the incident, Mothes and Werner surveyed the damage to their yacht.

"The first thing we did was make sure there was no water downstairs. We didn't know if the whale was coming back," said Werner.

The couple were contacted by other concerned sailors who had seen the accident, but they were fine.