A MARINE biologist has spoken of the battle to save tourists whose boat capsized in shark-infested waters off the South African coast, causing three to drown.

Sealife expert Alison Towner, originally from Ramsbottom, was on a neighbouring vessel when a 'freak wave' upended the nearby Shark Team boat.

Alison, 22, says the rescue effort, which involved crews from three boats plucking survivors from the waters off the coast of Gansbaai, was nothing short of a miracle'.

But three tourists - Americans Christopher Tal-iman, 34, Casey Scott LaJeunesse, 37, and 37-year-old Norwegian Kenneth Roque - lost their lives in the tragedy on Sunday.

Police have confirmed that the trio are believed to have drowned and though the waters are infested with great white sharks, they were not involved in the deaths.

Alison, a former Bangor University marine biology student who has been working in South Africa for around 18 months, said: "It was a complete freak disaster.

"There has never been anything like that happen in more than 50 years."

Her boat, Shark Fever, was moored alongside the Shark Team, which had been undertaking shark viewing dives for around three hours.

When the wave hit, Alison put out a mayday call to other vessels in the area, which is popular for shark-watching tours.

Meanwhile Alison and her crewmates pulled their own passengers, who were in a cage underneath the vessel, to safety.

The crew then assisted colleagues from the Shark Team boat, helped by another boat, owned by the White Shark Diving Company, which had arrived on the scene.

Alison said: "Some of the people were in the water for two minutes and everyone, apart from the three underneath the boat, had been pulled from the water within six minutes.

"It was a miracle that they got out of the water," said Alison, whose boyfriend was aboard the Shark Team boat.

"Everyone does have a perception of great white sharks, but when the boat capsized they were in the water with all the chub lines and oil and the sharks didn't touch any of them."

Alison, who works for a company called Marine Dynamics, has been back in the waters this week, in the wake of the tragedy.

Shark expeditions were suspended in the days following the deaths.

"It was a traumatic experience, but we have just got to get on with things," she added.

The Shark team vessel - a double-hulled catamaran - has been inspected by the South African marine authorities and police.