How a coach saved sinking US swimmer Anita Alvarez

American artistic swimmer Anita Alvarez was in danger of drowning after losing consciousness in the pool at the world championships in Budapest before being rescued by her coach Andrea Fuentes.

Spaniard Andrea Fuentes, a four-time Olympic medallist in synchronised swimming, jumped into the pool after she saw Alvarez sink to the bottom at the end of her solo free final routine.

"Anita is much better, she is already at her best. It was a good scare, to be honest," Fuentes told sources. "I jumped into the water again because I saw that no one, no lifeguard, was jumping in. I got a little scared because she wasn't breathing, but now she's fine. She has to rest."

It was the second time Fuentes has had to rescue Alvarez after she leapt into the pool during an Olympic qualification event last year and pulled her to safety along with the American's swim partner Lindi Schroeder.

Alvarez was taken on a stretcher to the pool's medical centre, with teammates and fans appearing to be in shock poolside, with some in tears consoling each other. A statement stated that Alvarez fainted due to the effort expended during the routine.

In a statement on the U.S. Artistic Swimming Instagram page, Fuentes said 25-year-old Alvarez would be assessed by doctors on Thursday before a decision was made on her participation in other team events.