Comment by dreamcompiler

> it's possible for a black hole to have a lower density than water

But that density is not homogeneous. It's much denser in the middle. As you cross the event horizon you wouldn't notice anything happening (as long as the BH is big enough that the tidal forces were small so you didnt get spaghettified). But things would feel very weird as you got closer to the middle.

Probably. Nobody has proved any of this but it seems likely.