The Story of Michelle:

Sailor Neptune appears at the beginning of SMS. Michelle is a lot like Amy in many ways. Michelle studies hard and also has powers that use water. Except Sailor Neptune's powers are much stronger then Sailor Mercury's. Sailor Neptune owns one of the three talisman to make the Holy Grail. The Deep Aqua Mirror.

Sailor Neptune's Powers

I haven't actually seen any of these powers yet because I live in Canada, so I'll just give an answer except I'll rephrase it in my own words.

*SMS Powers*

*Neptune Planet Power!*
Michelle says this to transform into Sailor Neptune.
*Neptune Tidal Wave Submerge!*
Sailor Neptune says this to create a big amount of energy from the oceans which forms the planet Neptune. Sailor Neptune heaves the energy at an enemy.

*SMSSS Powers*

*Neptune Crystal Power!*
Michelle says this to transform into Super Sailor Neptune.
*Submarine Reflection!*
Super Sailor Neptune says this to create a big amount of water from her talisman. The Deep Aqua Mirror.