Researchers from the University of Manchester, Politeknik Negeri Semarang, Israel Institute of Technology, and Khalifa University investigated floating photovoltaic (FPV) panels with natural convection cooling loops. Using a two-dimensional multi-physics numerical model, they analyzed thermal performance with pure water and 5.3 ppm Ag-water nanofluid as coolants. Pure water achieved an electrical efficiency of 15.45%, outperforming Ag-water nanofluid at 15.08% and standard FPV panels without cooling at 14.98%. The superior efficiency of pure water was due to its higher transmissivity in the critical wavelength range of 325–1125 nm, while Ag-water nanofluid reduced temperatures more effectively. The study also highlighted that coolant channel thickness impacts buoyancy-driven flow rates and panel temperature, emphasizing the importance of both thermal management and spectral transmissivity in improving FPV efficiency.