Even seen the footage of a test between a .50 BMG and a Katana? The blade split two bullets, deflected another, then shattered, IIRC.
EDIT: It'd be easier to tell if it were in color, but I think the "water flying all over" is actually metal shards.
EDIT2: Nevermind, didn't get far enough. Heh.
It makes me wonder, seeing how they're acting, if a bullet turns to liquid for a second upon a hard impact like that. The metal looks to be behaving that way as it sheds away.