Bluebottles halt Durban charity swim

They set themselves an almost impossible task, hoping to change public opinion about a sea creature feared by millions of people.

But in the end the Great Shark Swim was called off when 21 exhausted swimmers ran into a smaller oceanic peril - bluebottles off the coast of KwaZulu-Natal.

Known as the Mad Swimmers, they hoped to set a world record by swimming 100km in a day to raise funds for children's charities and call attention to the survival of sharks.

Before leaping into the sea south of Durban on Saturday, Mad Swimmers founder Jean Craven said their goal would not be attained without a helping hand from Mother Nature. They had hoped the mighty Agulhas Current surging down the coast of southeast Africa would provide extra swimming momentum.

Craven and Durban oceanographic consultant Lisa Guastella analysed information from satellites and floating data-collection "drifters" for months to determine the ideal weather, wind and current "window period" to swim.

The swimmers - 16 South Africans, four Israelis and a Spaniard - had hoped for ideal conditions, a current running at four knots. But that did not happen.

They rose at 2am and before daybreak were transported 20km out to sea near Park Rynie.

"We really were at the mercy of nature," said Craven.

"We needed a minimum of 2.2 knots per hour to attempt the record. Current forecasts for later in the week were rather uncertain, too, so we decided to go with the relatively good weather forecast, trusting current speed would pick up overnight."

The swim was aborted nine hours and three minutes later when they encountered a dense mass of bluebottles about 28km from the start.

"We would have loved to encounter sharks but it was bluebottles instead," said Craven.

"We hope this swim will encourage others to do their small part, too, to make this world a better place."

Craven said an estimated 100million sharks were killed a year, mainly due to the fishing industry, compared with an average of five human fatalities from attacks a year.

The Shark Specialist Group, an expert scientific group of the International Union for the Conservation of Nature, has evaluated the status of more than 1000 species of shark, ray and chimaera species and found 25% of them were threatened under the union's Red List of Threatened Species criteria.

Sharks and rays at highest risk of extinction were large-bodied species in shallow and heavily fished coastal waters. The group said at least 28 populations of sharks and rays had already gone locally or regionally extinct.