The location of large surface industrial zones along sea shores often competes with other coastal activities, such as recreational pursuits, fishing, nature reserves, etc. The construction of an artificial island in the sea, near the shore, is a solution to which it will perhaps be necessary to have recourse in the fairly near future. The design of such a project poses many problems particularly in respect of its impact on the environment. We present here the results of a study which examines this aspect. The problems are as follows : - influence of the island on the local wave climate, or swell, and consequent shoreline changes, - influence of the island on tidal currents and resulting evolution of the sandy sea bed, - dispersion of industrial effluents. The effect of the island on swell and on shore stability and the calculation of pollutant dispersion are approached by the use of mathematical models ; the effect of the island on tidal currents is analysed on a reduced scale physical model.