Years ago I read a book about black holes. It said it is theoretically possible to make a black hole from ordinary-density materials, like tap water. It would take a lot -- about the size of a galaxy IIRC. But it implies no singularity, so I guess you could be inside a black hole and things would seem normal. Can anyone confirm this?
EDIT: What I envisioned is water in the shape of a disk, rotating like a galaxy, and mass is added to it until it becomes a black hole. If you have water about 1 km thick, then at a radius of about 10^20 km the Swarzchild radius will be bigger. I'm wondering what happens at that point, viewed from the inside.
EDIT2: The example above would be about 100x the diameter of the Milky Way. So re-envision it as 100km thick and the same diameter as our galaxy. Secondly, the density of this "galaxy" is about 10^18 times that of a typical galaxy. So you would have to put the mass of a billion billion galaxies into one galaxy in order to witness the creation of a black hole from within.