Piranha 3D

[Ngjoko]

Well, not really. But it doesn't have to be silicon. But yeah, 70% gals in movies in general have fake ones.
If you really need to look busty and not showing too much flesh, grab a couple of oranges and stuff it in your bra. Or split a coconut in half and use those as bra. No matter how hard you move you'll have the same shape with a con, less bounce.