This study investigates the hydrodynamic behaviour of a modular Floating Solar PhotoVoltaic (FSPV) island developed by the National Research Council of Italy (CNR) and University of Naples Federico II and analysed in collaboration with Saipem S.p.A. The system is composed of hexagonal modules interconnected by universal joints, which allow dynamic adaptation to wave motion, all contained within a floating elastic ring. The hexagonal module behaviour is investigated first in the frequency domain using HydroD/Wadam; second with time domain analyses using OrcaFlex to assess its motions in operative environmental wave conditions. The ring hydrodynamic response is assessed using both frequency domain FFLOB numerical solver and Orcaflex time domain nonlinear analyses. Results show that the motions of the hexagonal module could be deemed acceptable for moderate sea state conditions, with viscous damping having a significant effect on motion reduction. For the ring, a reasonable agreement is obtained in both rigid and elastic modes, also validated with experimental data. While further studies are required, these findings provide a foundation for the development of FSPV systems.