Greenhouse gas emissions are primarily caused by the exploitation of fossil fuels as an energy source, and one way to reduce those emissions is to utilize renewable energies such as solar irradiation conversion. In the city of Istanbul, two Floating Photovoltaic (FPV) prototypes were installed in 2016 on Buyukcekmece Lake, a large body of water that supplies fresh water to the city, as a means of both reducing evaporation loss and generating electricity. The systems had capacities of 90 and 30 kWp, respectively. Additionally, a 30 kWp capacity Terrestrial Photovoltaic (TPV) system was installed to facilitate a comparison of electricity generation between the systems. FPV systems, which have been hailed as new alternatives to TPVs, are generally set up on calm bodies of water. Buyukcekmece Lake, however, is open to severe weather conditions, including wind-driven waves that can reach heights of 1.5 to 3.0 m, which can lead to unbalanced load distributions on FPVs and damage to the systems. Of the two systems that were installed, one of them had a semi-flexible frame, but that prototype ultimately failed as a result of wave action. However, a new design referred to here as a "fully flexible FPV system," held up under the severe conditions on the lake. The total amount of electricity generated by the first 90 kWp FPV system was approximately 17 400 kWh and the capacity factor was around 42% for a period of 467 hours between May 19, 2017 and July 4, 2017. Between November 21, 2018 and December 22, 2018, the second FPV system generated 309 kWh, while the TPV had an output of 365 kWh. The capacity factors for the systems were calculated as 14.51% and 17.15%, respectively. The most important finding of these studies concerns in order for FPV systems to operate safely in severe weather conditions that can result in unbalanced load distributions, the units that comprise the system must be able to float independently, and the system connections must be flexible. Moreover, based on the measured values it was found that in terms of electricity output, neither FPVs nor TPVs have a major advantage when compared to each other.