Site selection for fish farms is crucial for the sustainable development of the industry. Degradation of the environment, and interference with other activities, has to be foreseen and avoided as much as possible. Likewise, harm to the cultured animals due to a contaminated or inappropriate environment also has to be avoided. A careful study prior to any installation should be compulsory, and should consider aspects as: permit system regulations, conflicts with other water-land uses, local hydrographic conditions, water quality, terrestrial inputs, wave climate, wind patterns, seabed characteristics and dynamics, and accessibility and available facilities. The importance of each of these factors is considered. Moreover, the use of hydrodynamic and dispersion models will be presented, demonstrating their use as a powerful tool for coastal managers. Such managers have to decide on licences for fish farms, taking into consideration environmental affection and-or multiple pollutant effects (caused by the non-rational grouping of farms).