This dataset provides in situ measurements of water temperature (degrees Celsius), salinity (PSU), turbidity (FNU), chlorophyll-a fluorescence (micrograms per liter) in surface waters (~0.5 m). Measurements were made in the Atchafalaya and Terrebonne Basins on the southern coast of Louisiana from 2021-03-25 to 2021-04-22 as part of the Delta-X 2021 Spring campaign. During the field campaign, measurements were collected in multiple channels of varying width (from a few meters to >100m), near Delta-X intensive study sites, and in open bays and lakes and at few locations in the nearshore Gulf of Mexico. For each in situ collection, the measurements were collected using YSI ProDSS water quality probe.