Making holes into a mesh

Hey, so I was wondering, again, is something like this might be possible. like a week ago i saw a water splash made in unity, using mesh.vertices. So I thought, that that is kinda cool. So here comes the problem, i need to make a hole into a mesh, when a ball- with that playerBullet - touches it. I saw trying to do something, but i ended up in a crash, and some strange mesh disappearing :-).

So let me do it short. I need to make a small hole (i mean, big like the ball or something like) in a wall/mesh when some ball- with a tag - touches it.

• David.

PS: I searched all over the answers and google.com, and i have found nothing that i might need...just for the admins ;-)