'Step Up 3D' Chick
Skin & Bones on the Beach
12/19/2011 4:00 AM PST BY TMZ STAFF
"Step Up 3D
" star Sharni Vinson
showed off her alarmingly slender bikini body on the beach in Sydney this weekend.
The 28-year-old -- who is currently dating "Twilight
" muscleman Kellan Lutz
-- could really use a cheeseburger about now.
So, we gotta ask ...