Sienna Miller was reportedly sunning on a 
Malibu beach  over the weekend with a girlfriend when she headed for the water in  order to cool off.  Her skimpy tube bikini top headed south – exposing  the breasts of the actress.
She immediately righted the situation and headed back to dry land –  as captured by a member of the every vigilant paparazzi.  She was  spotted later that day with boyfriend 
Rhys Ifans.  The couple enjoyed a sushi meal at 
Nobu in Malibu.
Daily Mail has the full view nip shot of the actress and another as she tugs her bikini top back over her breasts.