Suspended sand transport plays a vital role in sediment dynamics, influencing sediment redistribution and morphodynamic processes in coastal and fluvial environments. Recent full-scale experiments were conducted in the Large Wave Flume in Hannover (GWK) to study the effects of varying grain size distributions in sand mixtures on suspended sediment concentrations under wave action. A horizontal test bed with sand mixtures of fine (d₅₀ = 0.21 mm) and coarse (d₅₀ = 0.58 mm) grains in different ratios was subjected to the same wave period (T = 7 s) but to two different wave heights (H = 1.0 m and 1.5 m). Suspended sediment concentrations were measured using a Transverse Suction System (TSS) and Laser In-situ Scattering and Transmissometry (LISST100C). The TSS utilized six steel nozzles positioned at heights ranging from 0.02 m to 0.52 m above the bed, while the LISST was installed at 0.5 m above the bed. Results revealed that increasing the proportion of coarse grains in the sand bed mixture significantly raised the suspended sediment concentrations, particularly under higher wave energy conditions, and influenced the formation of bedforms. Comparisons between TSS and LISST measurements showed consistent results, with the LISST slightly underestimating concentrations but demonstrating a strong correlation. These findings underscore the importance of grain size distribution in sediment transport processes and provide critical insights for refining sediment transport models, coastal management, and erosion control strategies.