Physical and chemical data were collected to characterize water-quality conditions in the Sakonnet River, a tidal strait located on the east side of Narragansett Bay in Rhode Island, from April 28 to November 11, 2018 and from June 19 to November 26, 2019. Specifically, the 2018 information in this data release includes: vertical profiles of water quality from 16 to 18 locations and data collected from three surface spatial surveys (moving boat surveys) designed to characterize near-surface water-quality conditions in the river. Temperature, pH, specific conductance, salinity, dissolved oxygen concentration and saturation, turbidity, and chlorophyll a data were collected with calibrated water-quality sensors. Water-quality profiles and moving boat surveys were conducted on July 26, August 28, and September 25, 2018. Similar to 2018, information collected in 2019 includes vertical profiles of water quality from three locations during three moving boat surveys of a single east-west transect using the same sensors as in 2018. Data were collected on August 15, 2019, at three different times during the tidal cycle. The dataset in this data release includes one comma-delimited test (.txt) file of all station locations, four .txt files of vertical water-quality profiles, four .txt files of moving boat surveys, and two tagged image file format (.tiff) files of map images showing 2018 and 2019 profile locations and example moving boat survey tracks. Additional data collected during the investigation are available from the USGS National Water Information System (NWIS). These include (1) continuous water-quality records from three monitoring buoy stations during 2018 (USGS station identifiers 413642071125701, 413252071131501, and 412932071124701) and from a single monitoring buoy station during 2019 (413642071125701) and (2) laboratory analytical results of water-quality samples collected from surface and bottom waters at the 2018 and 2019 continuous monitoring stations.