05/08/2015 10:25 BST | Updated 05/08/2015 14:59 BST

Natalia Molchanova, World's Greatest Freediving Champion Feared Dead After Going Missing Off Formentera Island

Russian freediving champion Natalia Molchanova is feared dead after she went missing off the coast of a Spanish Balearic island.

International diving federation AIDA said in a statement that Molchanova had been diving without fins at a depth of 30-40 meters (98-130 feet) off the coast of Formentera island when she failed to resurface on Sunday.

Maritime rescue coordinator Miguel Chicon said the operation was "very complicated" because the 53-year-old Russian could have become trapped by weights she was wearing at the time of the dive.

natalia molchanova

Natalia Molchanova has been missing since a dive on Sunday

A submersible robot was brought in to expand the search on Tuesday.

Molchanova was among the most decorated competitors in free-diving, a sport in which participants swim as deeply as they can while holding their breath.

She held 41 World Records and was a 23 time World Champion in the sport.

The mother-of-two boasted a 9 minute breath hold, could dive to a depth of 101m using a fin and swim a distance of 234m, also with a fin.