[EDIT] Changed W and R into offensive based abilities. Reduced Passive by 4%.

Concept: Water based Mage. Can take more hits than the average caster with decent Defense, Magic Resist, and Health.

Mage, Ranged, Support

Passive:
Shell Armor - Increases Defense and Magic Resist by 3%

Abilities

Torrent - Shoots duel jets of water in a given direction pushed back those in it's path to the end of the water jet. Slows down units and does moderate damage.

Whirlpool - Create a powerful maelstrom in target area sucking enemies into the center before bursting at the center dealing damage.

Hydration - Attack, AP, and Attack Speed are all reduced 10% while gaining Health and Mana as well as increased Health and Mana regeneration in the duration of use (3-6 seconds)

Water Siege(Ult) - Slams columns of water to the ground in a large radius dealing significant damage.

Stats

Low - Movement, Damage, Attack Speed
Medium - AP, HP, Mana
High - Defense, Magic Resist

Uses - Whirlpool is a nice setup for both Torrent and Water Siege. Whirlpool and Torrent can buy some time for Hydration or a getaway.

I like the idea, but some things are too strong.

passive: too much true damage reduction. 1st true damage cannon't be reduce that's the point and second 7% is like having 7% more resistance at start that is pretty good while being a mage but not if he is too resistant. 4% would be ok don't forget it can be 8% total with the final defensive mastery that grants 4%.

For others ability i would need more info to tell anything but looks ok. Good idea!

this champ is everywhere
his e+r are situational and give stats not for standard "casters"
the bonuses given dont really add up
passive is op

he only has one "spell"- his q
his w requires him a caster to be in the middle of a fight...... steam=/= water its vapor

there's not much snergy with this champ that i can see, and is lacking a hard cc meaning he'ff be chewed up

only thing i can really see him doing is tanking poorly or backdooring