Posidonia Oceanica is an endemic Mediterranean plant with the same external organization as the superior plants. It has roots, stem, leaves and capacity to produce flowers and fruits with seeds. It forms large underwater meadows that are an important part of the ecosystem. The fruit is free floating and known in Italy as "the olive of the sea". The plants of Posidonia oceanica grow forming wide meadow, for an optimum growth it needs transparent waters. For this reason, the presence of dense and large meadows is a clear sign of the quality of its waters. The presence of Posidonia Oceanica proves the quality of the water represented in this series of paintings, with the focus is on the refraction of light on a soft background, the sky at different times of the day.