This volume presents some of the most recent progress in the mathematical theory of fluid mechanics. The eight papers herein originated in a series of seminars held in 2011 at the Chinese Academy of Sciences in Beijing. Among them are Nicolas Burq on the wellposedness of the water wave problem with rough data, Jean-Yves Chemin on the wellposedness of the Navier-Stokes system, and Isabelle Gallagher on the semiclassical limit of a geostrophic system. This third volume of the series is a good reference for those working on nonlinear partial differential equations, especially as applied to fluid mechanics equations and micro-local analysis.