"Version: 20171201"--Title page verso."A Morgan & Claypool publication as part of IOP Concise Physics"--Title page verso.Includes bibliographical references.1. Introduction -- 1.1. The fluid approximation -- 1.2. The hydrodynamic equations2. Some basic concepts -- 2.1. Visualisation -- 2.2. Sound waves -- 2.3. Compressibility -- 2.4. Rotation of fluid elements -- 2.5. Gravitationally stratified…