Harvesting underwater Solar energy using photovoltaic (PV) technology leads to an innovative approach to utilize it in monitoring various underwater sensors, devices, or other autonomous systems using modern-day power electronics. Another huge advantage of placing PV cells underwater comes from the fact that the water itself can provide cooling and cleaning for the cells. Such advantages come with many challenges and constraints due to the underwater spectral change and decrease in Solar radiation with an increase in water depth. In this work, an experimental set-up has been realized to create an underwater environment and further characterized in the indoor environment using the Solar simulator. Moreover, the transfer of Solar radiation through water and the performance of amorphous silicon Solar cell underwater up to 0.2 m has been analysed in changing underwater environments. This investigation shows a better understanding of solar radiation underwater and the amorphous silicon solar cell underwater at shallow depths with considering the water depth up to 0.2 m, salinity 3.5%, total dissolved salts, and other impurities affecting the solar radiation and the performance of amorphous silicon Solar cell in underwater conditions. In addition to that, the maximum power output P-max of amorphous silicon Solar cell is 0.0367 W at 0.2 m in the case of DI water. In contrast, in real seawater and artificial seawater with 3.5% salinity, it shows 0.0337 W and 0.0327 W, respectively.