Spain has scaled back the search for world free diving champion Natalia Molchanova who went missing during a weekend dive near the holiday island of Ibiza as hopes faded on Thursday that she will be found.

"You can't search indefinitely. We will search on the surface until Sunday," a police spokesman on Spain's Balearic islands said.

"Bodies normally rise to the surface but in this case since she used lead weights we don't know what will happen."

"We are now only searching on the surface. The underwater search has ended," he said,  adding that the record-breaking Russian sportswoman's body may have been swept away by the current.

Two boats were combing the area on Thursday for signs of Molchanova, the most decorated free diver in the world, with 41 world records and 23 world championship titles.

Molchanova failed to resurface after diving without fins to a depth of 30-40 metres (100-130 feet) off the coast of Formentera island, adjacent to Ibiza, on Sunday, the international diving federation AIDA and her family said in a joint statement.

Spain's rescue service deployed a helicopter, boat and several divers to search for the 53-year-old Russian, who was wearing weights at the time of the dive.

Her family also hired an underwater robot capable of searching a radius of nearly 500 metres to search for her.

It was a modest dive for Molchanova -- her record dive without the use of fins is 71 metres, set in May in Egypt.

AIDA said Molchanova became separated from her thee colleagues and probably got caught in a strong underwater current.

Free divers dive without scuba equipment, sometimes to great depths, relying on their ability to hold their breath.

Molchanova could hold her breath for nine minutes and dive to a depth of 101 metres (333 feet) using a fin, according to AIDA.

Based at Moscow's Russian State University of Physical Education, Sport, Youth and Tourism, Molchanova abandoned competitive swimming at the age of 20 to raise her two children, Alexey and Oksana. She started free diving when she was 40.
Source: AFP