Star Dress: Aquarius Form is one of several forms of the Star Dress Spell.
The user takes on an appearance based on Aquarius' own, aquiring a bikini top that sports a zigzag design; frilled, dark sleeves that are secured around their upper arm by a ribbon; and a frilled, dark miniskirt; around said miniskirt is a ribbon that is tied in bow to keep it secure. Additionally, the user's hair becomes tied up in pigtails and they are given sandals to wear. Aquarius' zodiac sign is located between the user's collarbone whilst in this state.
Water Magic (水系各種魔法 Mizu Kei Kakushu Mahō): After sacrificing Aquarius' key to summon the Celestial Spirit King, Lucy was bestowed the Magic of Aquarius by the Celestial Spirit King, which allowed her to both consciously and unconsciously make use of her friend's powers.