User blog comment:Yountoryuu/The Wikia's SBS/@comment-3177945-20110202235206/@comment-3279487-20110203013135

I asked that myself, but I think I can answer you about Raftel... even if, for example, a Navy ship can go through the Calm Belt you still need a log pose and a log pose is set island by island, so you can't point straight to the end, but you have to start setting your log pose from the first island. Even if you start from the last island known (going there with an eternal pose) you should assume the last part of the grand line is VERY difficult to sail, or maybe (a guess) the log pose doesn't work normally (otherwise it shouldn't be so difficult reach raftel...). But I still don't know how you can exit (safely) the grand line or go in another blue, especially for a pirate...