According to the World Meteorological Organisation, only 2.5% of the total volume of water in the world is freshwater. One of the most important sources of freshwater lies underground, and is known as groundwater. The use and exploitation of these reservoirs have increased in response to increased water demand, as a supplementary source to surface water (rivers and lakes). In some places, groundwater can be the only source of freshwater. Coastal aquifers, which are underground sources of freshwater in coastal areas, are a very important source when considering the water resources in areas bordering the sea. These sources are in contact with or close to saline water, and therefore, the intrusion of salt water caused by both natural and man-made processes has become a major threat to the sustainability of such reservoirs. This process is known as salinisation. The development of tools to facilitate prediction of the behaviour of these aquifers under different conditions is crucial for the adequate management of groundwater systems in coastal areas.