This dataset contains: (1) Raw movies (format: .mp4, 6-megapixel, 20 fps) of experiments conducted in the outdoor laboratory channel at the Institute of Hydro-Engineering Polish Academy of Sciences, during March-April and June-July 2025. Experiments cover different scenarios with either macroplastic accumulation or remobilisation; excel file lists every scenario's details: date, discharge, initial water level, number and type of items used. There are 5 cameras, txt file and a report that describes camera positions, which were situated above the channel, along its 50 metres length. (2) Raw data from the hand electromagnetic velocimeter and acoustic Doppler velocimeter, and results of water velocity measurements conducted after both campaigns for corresponding water discharges, done for 3 crossection along the channel (depicted in the additional graph). (3) Raw data from the meteorological station (installed next to the middle of the channel, on the 5 m pole, coordinates 470265.31 E and 727243.41 N) recording wind speed components in the southern and eastern directions in .dat files from days when the experiments were conducted. Txt file with instruction how to read the data. (4) Bathymetry data of the channel where experiments were conducted, with visualisation figures and excel file with coordinates and elevations, suitable to create a DEM mesh.