We consider three particular free-surface flows in irrotational 3D fluids; they are the vortex sheet with surface tension, the water wave, and Darcy flow. We describe a common framework in which the equations of motion for each problem can be formulated. This involves choosing a favorable parameterization of the free surface and convenient dependent variables. After the problems have been formulated in this manner, energy estimates are possible. Well-posedness of the initial value problem in each case follows from the energy estimates.