The dataset includes physical and biogeochemical measurements of water properties, meteorological data and biogeochemical measurements of sediment parameters. Temperature, salinity, turbidity, oxygen, nutrients, dissolved organic carbon/total dissolved nitrogen (DOC/TDN), particulate organic carbon/particulate organic nitrogen (POC/PON), contaminants and pH were measured at most of the data collection sites, with additional biogeochemical measurements collected at various locations. Temperature, salinity and nutrients are available for virtually all data collection campaigns. The data were collected in a number of estuaries around the UK between 1993 and 1997. The Humber estuarine data set was collected during a series of 33 campaigns on the EA vessels Sea Vigil and Water Guardian in the Humber, Trent and Ouse systems at approximately monthly intervals between June 1993 and December 1996. The measurements were taken over two or three one-day cruises that covered the estuary from the tidal limits of both Trent and Ouse to Spurn Point. Instrumental and sample data are available from a series of fixed stations that were sampled during every campaign. The Tweed estuarine data set was collected during a series of 13 campaigns using RV Tamaris and a rigid inflatable vessel at approximately monthly intervals between July 1996 and July 1997. Data were collected throughout the tidal reaches of the River Tweed. The dataset forms part of the NERC Land Ocean Interaction Study project. Key investigators for this LOIS sub-project included Plymouth Marine Laboratory. The data are held in the British Oceanographic Data Centre project database.