User blog comment:IamJakuhoRaikoben/Chapter 446: The Land Abandoned By God, Review./@comment-5303512-20150727051623/@comment-7418318-20150729185804

There is a difference. In all the other Star Dresses Lucy used all the powers consciously. But in Aquarius mode, the water-shield came up without Lucy casting it. She only noticed it after it was in place and believed it was Aquarius who cast it.

I guess we'll never know if it was done subconsciously by Lucy or if either the Celestial Spirit King or Aquarius activated the shield through Lucy, but it certainly was different from what we've seen in other Dreses.

But ultimately I too think that this Aquarius' mode was a Star Dress, only with a few temporary additions courtesy to the Celestial Spirit Kings direct intervention.