Freediver Natalia Molchanova's 'amazing' achievements
Natalia Molchanova, the 53-year-old Russian champion freediver, is feared dead after going missing on Sunday.
Ms Molchanova, who holds 41 world records, was diving for fun off Formentera, a Spanish island near Ibiza, when she failed to surface.
Stephan Whelan, founder of a freediving website, said she may have been caught up in strong underwater currents.
He paid tribute to her "amazing" sporting achievements.
Footage courtesy of Daan Verhoeven