Oops! The moment Sienna Miller's bikini malfunction left her showing a bit TOO much

The surf was up in California yesterday, but unfortunately for Sienna Miller, she was caught with her skimpy bikini top down.

The actress revealed more than expected as she eagerly raced into the waves to cool off after lounging in the sun, with her tiny strapless number slipping down around her waist.

GI low: Sienna Miller’s bikini top fell down as she hit the waves in California yesterday

Adjustment: Sienna corrects her wardrobe malfunction

Realising her moment of over-exposure, she quickly pulled her top up and returned to the sand with a female companion.

Sienna is, of course, no stranger to baring flesh, and last year filmed nude scenes for her upcoming Hippie Hippie Shake set in the Swinging Sixties.

Later she met up with her boyfriend Rhys Ifans for a sushi feast at Nobu in Malibu, where, thankfully, they were both fully clothed.

Taking the plunge: Sienna cools off after with a quick dip

The pair, who have enjoyed a string of luxury holidays since they began dating last year including a trip to Mexico, recently reunited in LA.

She was previously filming the action movie GI Joe in Prague while Rhys, 39, was working on Richard Curtis's new movie The Boat That Rocked in Southampton.

Summer loving: a day earlier, Sienna and her rotund companion Rhys enjoyed a romantic afternoon together

But the couple, who are rumoured to be planning a wedding, kept in touch with long-distance calls – albeit in Welsh.

"Sienna is always on the phone to Rhys and sometimes she misses him so much she just gets on a plane back to Britain to see him," an on-set source said.

"It's very sweet – whenever she says, 'Darling I love you,' she says it in Welsh – 'Fy anwylyd, rwy'n dy garu di'."

Fun in the sun: Sienna certainly made a splash during the outing