The data set includes grain size distribution of sediments from the reef island Langkai, SW Sulawesi, Indonesia. The data was collected in order to reconstruct the Holocene and modern (sediment) dynamics over the past ca 6,000 years. Sediment samples were obtained from sediment cores taken by percussion drilling and hand-held (Auger) coring in May 2016 and July 2021. Laboratory analysis of the sediments and shoreline analysis were carried out between 2021 and 2023. The grain size distribution was determined by dry-sieving of the bulk sample into fractions following Wentworth (1922).