Understanding particle behavior in the aquatic environment is fundamental to unraveling key processes in biogeochemistry, sediment transport, and ecosystem dynamics. Since 1995, Sequoia’s LISST and Hyper instruments have become important tools for quantifying particle size distributions (PSDs), concentrations and optical properties in situ. How do particle dynamics differ across aquatic environments as diverse as rivers, tidal flats, fjords, continental shelves and the open ocean —and what can Sequoia instruments reveal about these differences?