Granted. You now operate a dam.
The Monkey's Paw
Want to make a wish? Just ask the Monkey's Paw! No strings attached*.
(*) Satisfaction not guaranteed. Wish may backfire unexpectedly.
Just create a post that starts with "I wish ___" and wait for other users to write how your wish didn't turn out how you expected.
If you're feeling inspired, you may even use the wish as a sort of writing prompt.
Example:
Title: I wish for more wishes.
Answer: Granted. A piece of paper the size of a business card appears in your hand with 4 dotted lines for you to fill out your wishes and a little checkbox in front of each. Now to find someone who will grant those...
Granted, you must consciously control all the water inside your body at all times. If you break concentration for even a moment, you might accidentally rupture all your cells.
Granted. The water gets the power to control you back.
Everything you use your power, your hair falls out. It can grow back, but it takes a while.
Any water you control smells increasingly like piss the more you interact with it. As a byproduct, you generally start to be kind of a smelly guy