User blog comment:Omega natsu2/Future Matchups!/@comment-3424593-20140414002654/@comment-2214433-20140414222048

But creating water is not messing with Zaraki's body directly. He had Isane imagine Vizards' deaths, too. That would also explain why he cannot just imagine entire SS dead. There must be some kind of a limitation to his ability.

Or it's a plothole :)