By watery, I assume you mean the body is lacking. You can typically tell how much body you're going to have by the final gravity reading. You're on the lower end of 1.012, which means it's ~12 gravity points above what plain water would be, so technically it isn't a whole lot but it is definitely noticeable (and frankly, about standard for a wheat beer). Carbonation will help add mouthfeel to the beer, but it will only take you so far. If you want to increase the body of the beer, you'll need to add more unfermentable sugars (next time obviously) to get the gravity higher. During your next brew, check the FG of the recipe and see where it lands. Based off what your current wheat beer will taste like after carbonation, take down some notes on the mouthfeel and body. You can use those notes as a comparison against future recipes' FG to tell if it is going to be more or less than your current beer.
It's also worth noting, your recipe is a standard wheat beer, which is typically light in body.
John Palmer has a good writeup on this: http://www.howtobrew.com/section3/chapter15-3.htmlhttp://www.howtobrew.com/section4/chapter20-1.html