I think the title says it all... Water Control/Hydrokinesis doesn't seem to be available even though many characters in comics display various levels of this ability (from the Atlanteans of DC shaping water into various forms to characters like Marvel's Hydroman who are made up of living water).
Now, some Body Control powers can simulate the effects of being made of water, such as Intangibility (for things being able to pass through the character rather than the character passing through objects) to Elasticity, Shapeshifting and even Size Alteration to represent the maliability of the form. However, there are no powers that really represent the direct manipulation of water, such as water blasts or the creation of waves and such. I guess Weather might be a possible interpretation, though most Hydrokinetic characters don't actually cause storms and such in most cases (even if they do draw on ambiant moisture in the air).
I know I could probably create an Invented Power (though I feel a Water Power should fit in the Material Category rather than Halmark as suggested in the rules), but I wanted to see if I was overlooking a less obvious power that might be suitable in this case.
I think that Weather is technically supposed to include water, but my personal solution was renaming Weather on the character sheet to Water, and treating it as a material power. Otherwise, if a character has both Fire and Cold, I could see them actually being a water manipulator. Fire reflects steam, cold reflects ice, and both can represent it in liquid form.
Transmutation feels like it could be used for this regarding water manipulation. If you explicitly want a power called Water I'd say it falls under Elemental/Energy or Materials powers.
I think the best thing to do is just make a power called "Water" under the Elemental category, assuming the character is generating and controlling water, shooting water blasts, etc. If they turn into water, I'd suggest they take the Self Control powers that describe that (Elasticity, Intangibility, Size Changing... Part Detachment?).
Actually, it might work better as a Material... it seems to me that the Elemental/Energy category is better for things similar to damage types in the card game (especially since you can take immunities to Energy/Elemental types). For instance, I don't really see someone being "Immune to Water damage!" and I can't make sense of "When you would take Water damage, heal that much instead!" So... yeah, Materials is probably a better Category.
I dunno, Bubbles picked up the ability to be healed instead of harmed by Bubbles damage.
Elemental is more about creating and attacking, and Materials is more about controlling. It might make sense to take it as either or both.
Most Element/Energy powers tend to deal with things that are not physical as such (such as fire, infernal or radiant) while Material deals more with physical substances, such as stone, metal and plants. Basically if you can hold it in your hands normally, then it is more likely a Material rather than Element/Energy. That said, there does seem to be overlap between the two categories... with Cold including things like Ice and Weather creating rain and such.
I was actually thinking of a character more like Aquamaria or Hydroman that are both made of "living" water as well as being able to control water... basically a Water Elemental of sorts, when I noticed there wasn't any power that actually controlled water as such.
As for using both Fire and Cold to represent water... it seems rather inefficient to use two powers to represent one, especially when one of those powers is often seen as the opposite of the power you are going for.
Reading what you have now put down about your character, I'd suggest taking Weather and renaming it to water. Manipulation of water vapor or natural phenomena seems very much to be an 'elemental' thing, as opposed to using it as a material. As far as the properties of living water itself, that sounds like a couple of different self control powers could be applicable.
I'm thinking more or a Control Power than Elemental/Energy... more of clasic waterbending that requires a ready source of water than manipulating watervapor in the air to generate their own watersource. It may not be as flashy as being able to create water sponateously like the aliens from the Dr. Who episode "The Water of Mars", but I think that fitst better for the character I am going for.
I am wondering though why the deigners overlooked this often possessed (though also often overlooked) power.
Then just make a Materials Power called Water. It might be because Water is most often folded into another power.