User blog comment:IamJakuhoRaikoben/Chapter 474: In the Moment of Complete Silence, Review./@comment-27792306-20160222233857/@comment-83.165.100.55-20160223131000

As long as we can see, Juvia is kinda different from other mages because she was born with the hability of using water magic even unconciously, as it was shown when she made rain when she was living in the orphanage, meanwhile others were teached like Gray or Romeo, so his water body is active unless it had been desactivated by other magic or had taken an attack that affects his water body(like electric magic)