Brody Jenner helped save Avril Lavigne's life.

The 'Girlfriend' singer was knocked off her surfboard during a lesson in Malibu, California, and it was left to her beau of three months to run into the sea to rescue her.

A source told America's Star magazine: "A big wave flipped her into the water upside down. Brody swam over and dragged Avril to shore, but she'd had the wind knocked out of her - she'd swallowed a bunch of water and was coughing.

"When Avril realised what happened, she was so thankful Brody was there to save her."

Avril and Brody began dating earlier this year and although they kept quiet about their relationship to begin with, Avril recently drunkenly declared her for Brody while singing karaoke.

The 'Complicated' hitmaker - who filed for divorce from her husband, Sum 41 rocker Deryck Whibley, last October - grabbed the microphone at the Bank nightclub in Las Vegas last month and wasn't shy about her feelings.

A source said: "They were having a blast. They were taking shots with friends including Olympic snowboarder Shaun White, grabbing the microphone, shouting, 'Jager shots' and making the crowd go wild."

The 25-year-old pop star even shouted, 'I love you, Brody!' on the microphone.

Since splitting from husband Deryck - who she was married to for three years - Avril has been romantically linked with actor Wilmer Valderrama and oil heir Brandon Davis.

Brody was most recently dating Playboy playmate Jayde Nicole, but they split in December.