The harbor area plays a crucial role in maritime traffic, port management, and ensuring navigational safety, making it essential to adequately protect this area. Floating breakwaters are often used as a means of protecting the harbor and vessels in ports, so it is crucial to accurately assess the transmission of wave energy. The aim of this study is to examine the accuracy of the formula for estimating the wave energy transmission coefficient proposed by Ruol et al. in 2013. for a floating breakwater of the π-type under the influence of spectral waves and to analyze the effect of water depth on the transmission coefficient. Measurements were conducted in a wave flume using a 1:21 scale model of a π-type floating breakwater. Incident and transmitted wave parameters were measured using eight measuring probes. Based on the measured wave data, the transmission coefficient was calculated. Data analysis revealed that an increase in water depth causes an increase in the transmission coefficient. It was found that the formula proposed by Ruol et al. in 2013. underestimates measurements by 25% for small values of Tp/Th (1.0<Tp/Th<1.20), while for larger Tp/Th values (1.30<Tp/Th<1.60) and shallow depths, the formula overestimates by 15%. However, for large depths within the same Tp/Th range, the formula is almost entirely accurate. Lastly, a polynomial was derived that relates the peak wave period to the natural heave oscillation of the breakwater with the transmission coefficient measured in this study.