User blog comment:FairyRaven/Fairy Tail Chapter 396: Air, Review and Commentary/@comment-74.61.219.92-20140813063447/@comment-74.61.219.92-20140814065914

Actually the explanation for Horolgiuum was when there is a high state of danger in which case Poison water and death tops the list. He also wouldn't sink considering he didn't sink in the Lava the arc previous to this. He also has arms for swimming. He doesn't need air either.