The article describes an industrial application of a vision based 3D scene reconstruction process. The images come from independent cameras whose locations are unknown and which are placed indifferently in two different media (i.e. underwater or in the air). This process is currently used in the Poseidon system (see http://www.poseidon-tech.com) to realize an automatic CAD model of a swimming pool. Poseidon is the first computer system in the world to help in the prevention of drownings in public swimming pools. We have evaluated the reconstruction accuracy based on synthetic scenes as well as real ones. In the case of real data, results are compared with measurements made by a surveyor (with a telemeter) and demonstrate high accuracy in 3D localization and reconstruction. Lastly, it proves that computer vision modeling can be efficiently used for real time applications.