This dataset contains paired optical and biogeochemical properties sampled in the Belgian Coastal Zone and inland waters of Flanders, Belgium, for the growth season period (March to October) of 2017, 2018, and 2019. This dataset was collected to support: (1) development and validation of hyperspectral algorithms for aquatic retrievals with in situ instrumentation; (2) development and validation of hyperspectral algorithms for aquatic retrievals with Earth Observation; (3) development and validation of multispectral algorithms and aquatic applications to high spatial resolution sensors. The data were collected over a series of short campaigns, with variable frequency depending on the water system and sampling year. The systems sampled were lakes, a lagoon, an estuary and coastal waters. The data consist of three types of data:I - Inherent Optical Properties:- Spectral CDOM absorption coefficient (< 0.45 μm; cuvette): (A) Measured, (B) Fitted to hyperbolic model, (C) Hyperbolic slope;- Spectral particle ... : Folder description: ./anc = Ancillary parameters:./anc/anc_metadata.csv : Station metadata (system, position, time, platform, depth)./anc/anc_observation.csv : Field notes./anc/anc_sun.csv : Local Sun zenith angle, azimuth and atmospheric pathlength./anc/gis = Geographical Information System data:./anc/gis/anc_gis_points.shp : Station points and metadata (LonLat, WGS84)./anc/gis/anc_gis_points.kml : Station points./iop = Inherent Optical Properties (IOPs):./iop/iop_ag_meas.csv : Spectral CDOM absorption coefficient (measured)./iop/iop_ag_fitted.csv : Spectral CDOM absorption coefficient (fitted to hyperbolic model)./iop/iop_ag_shg.csv : Spectral CDOM hyperbolic slope./iop/iop_ap.csv : Spectral particle absorption coefficient (measured)./iop/iop_ad_meas.csv : Spectral de-pigmented particle absorption coefficient (measured)./iop/iop_ad_fitted.csv : Spectral de-pigmented particle absorption coefficient (fitted to exponential model)./iop/iop_ad_sed.csv : Spectral de-pigmented particle exponential ...