The ocean generated beneath you has no collision. You can pass through. You could move in other directions if you could find the ones that don't kick you from the server since 32000000 is the maximum you can go in all directions.
+/-30000000 by +/-30000000 is where the actual world ends. From there to +/-32000000 by +/-32000000, the world generates fake chunks which aren't actually there and aren't complete. Moving outside this area gives an Illegal Position error. You can use an Eye of Ender to tell which way to move without getting disconnected/title screened. If you load the save up after illegal Position, you'll be within the bounds of +/-32000000 by +/-32000000, so no problem there.
More chunks generate outside the legal position area, by they appear to also be ghost chunks and they can't be explored, at least not unless you modify the game. But it probably wouldn't be much more interesting than the rest of the ghost chunks.
Poll