In this paper submerged photovoltaic systems (PVSs) are investigated with regard to the efficiency increase of PVS under high irradiance and ambient temperature; in particular, the optical and thermal effects are studied by means of experimental tests and mathematical models. The increment of efficiency through the cooling effects is evaluated. The PV panel performance of a submerged photovoltaic panel is investigated at different water depths. Experiments results on crystalline silicon panels are used to validate the models. (c) 2011 Elsevier Ltd. All rights reserved.