The aims of the book are to provide people who want to use hydro-informatic systems with knowledge on the basic principles, the capabilities, the different hypotheses and limitations. This knowledge is essential to ensure a safe use of software and reliable studies and to supply full explanations to people who want to implement or improve such hydro-informatic systems. This book is divided in to two main sections, the first deriving and presenting the basic equations of Fluid Mechanics. This part will provide the theory for understanding the dynamics of tides, tsunamis, storm surges, floods, bores, dam break flood waves, density driven currents, hydraulic jumps, and other flows in the environment and the second, explaining how these equations are solved with computers, mostly with the example of the Telemac hydro-informatic system and the Finite Element Method (FEM).