All sediment samples were obtained from Helgoland Roads (54.18°N, 7.90°E), which is located between the main island and the dune from Helgoland in the North Sea, German Bight, by scientific divers of the Alfred Wegner Institute (Bremerhaven, Germany) using push cores. Repeated sediment sampling was performed on a total of nineteen sampling dates in 2018 and 2019. Particle-size measurements were performed in the Particle-Size Laboratory at MARUM, University of Bremen with a Beckman Coulter Laser Diffraction Particle Size Analyzer LS 13320. Prior to the measurements, the samples were boiled with approximately 0.3 g tetra-sodium diphosphate decahydrate (Na~4~P~2~O~7~ * 10H~2~O, 3 min) to destroy aggregates. Sample preparation and measurements were carried out with deionized, degassed and filtered water (filter mesh size: 0.2 µm) to reduce the potential influence of gas bubbles or particles within the water. The obtained results provide the particle-size distribution of a sample from 0.04 to 2000 μm divided in 116 size classes. The calculation of the particle sizes relies on the Fraunhofer diffraction theory and the Polarization Intensity Differential Scattering (PIDS) for particles from 0.4 to 2000 µm and from 0.04 to 0.4 µm, respectively. The reproducibility is checked regularly by replicate analyses of three internal glass-bead standards and is found to be better than ±0.7 µm for the mean and ±0.6 µm for the median particle size (1sigma). The average standard deviation integrated over all size classes is better than ±4 vol% (note that the standard deviation of the individual size classes is not distributed uniformly). All provided statistic values are based on a geometric statistic.