The motion of both internal and surface waves in incompressible fluids under capillary and gravity forces is a major research topic. In particular, we review the derivation of some new models describing the dynamics of gravity-capillary nonlinear waves in incompressible flows. These models take the form of both bidirectional and unidirectional nonlinear and nonlocal wave equations. More precisely, with the goal of telling a more complete story, in this paper we present the results in the works [14,25,26,28,[30][31][32] together with some new results regarding the wellposedness of the resulting PDEs. Contents 1. Introduction 2. Models of surface waves in viscous fluids: truncation in the steepness 3. Models of surface waves in perfect fluids: truncation in the steepness 4. Models of internal waves in perfect fluids: truncation in the nonlocality 5. Numerical simulations for the inviscid water wave models 6. The question of well-posedness Acknowledgments References