I know from experience Concerta's are a bitch to crush, they may be the same active ingredient in Ritalin (Methylphenidate) but Concerta tablets were designed in a way that makes it much more difficult to abuse by breaking the time release. I remember trying to crush a Concerta tablet in between some paper on concrete using a hammer and all it did was flatten out.

If you leave it in water it has to dissolve eventually.