looks good to me. Although if I were to give advice, I would say don't try to memorize those kinds of formulas. Instead, try to remember a method for setting these types of problems up. Usually this involves some form of considering a small "slice" of water of width [itex]\Delta x [/itex] and finding the small amount of work [itex] \Delta W [/itex] and then summing up over the entire volume of the water.
this method might seem tedious for simple problems, but it might give you a better understanding of what is really going on here.