The official definition of the grit levels of sandpaper
goes something like this:

40-60 coarse
80-120 medium
280-320 extra fine
360-600 super fine

The highest number I've found is the 600.

But in several references to waterstones I've seen
the numbers 1000 and higher, maybe even
3000. If this is on the same scale as above,
it would imply that the waterstones are much
finer than "super fine". Can this be right?

My question is: Is the same grit scale applied to
waterstones and sandpaper or do waterstones
have their own scale?

The reason I'm asking is because I'm considering
trying to sharpen my tools with sandpaper (the
Scary Sharp method).