The Deep Aqua Mirror was Sailor Neptune's talisman. She could use it to perform the attack Submarine Reflection, and also could use it to reveal truth.
In the anime, the Mirror was found sealed within her pure heart. When the Mirror was brought together with the other talismans, the Space Sword and the Garnet Orb, it produced the Holy Grail. In the manga, Sailor Neptune already had the weapon when she first appeared, and instead of summoning the Holy Grail, the talismans summoned Sailor Saturn.
Sailor Neptune loaned the Mirror to Sailor Chibi Moon during the Dream arc of the manga. Sailor Chibi Moon later used the Mirror to learn the location of the Outer Senshi and, using the command "Submarine Mirror," teleported to them.
In all versions of the series, the Deep Aqua Mirror was a hand mirror with a golden handle and frame. In the anime, the back of the Mirror was deep aqua green and had the Neptune symbol upon it.
- In the musicals, the handle of the Mirror had a small slit where the actress could insert her index finger to make it easier to hold.
- The three talismans were based on the three imperial treasures of Japan. The mirror was said to represent wisdom.