It is nothing to "travel" in and it is not a fourth dimension.
I actually like to say that time doesn't exist!
"Time" is mostly a concept made by humans for their minds not to confuse and I think that most people have a wrong idea about what it is.
Neither is there a way to directly measure it; one can only measure the EFFECT of it.
And the closest thing we can come to "time travel" is what we do every day!
And as I said, time describes the speed of PHYSICAL reactions but our mind is most likely NOT what we consider "physical". Which means physicists are probably wrong in their idea about using a black hole to travel faster forward in time!
While the body near the black hole might have slower physical reactions which would make it age slower than the bodies outside the black hole its MIND may still perceive "time" the same way. Which means that the consciousness of that body will experience this as ultra-slow-motion and quickly get bored beyond belief!
So though the body may not have aged when exiting the black hole I don't think that it would FEEL like it had traveled in time.
And being near a black hole would crush you anyway...