This data set contains temperature, salinity, oxygen, fluorescence, turbidity, currents, and lagrangian drift data collected in the bay of Sept-Îles, on the north shore of the Gulf of St. Lawrence, Canada. Five sampling campaigns were conducted from May to September of 2017, to assess seasonal variations in the oceanographic conditions. An additional campaign was conducted in May 2018, focusing on the measurement of currents. These surveys covered the inside of the bay and the nearby archipelago. The bay of Sept-Îles has recently been the subject of a multidisciplinary study by the Canadian Healthy Oceans Network (CHONe II) because it is a heavily industrialized and urban coastal area at Canadian midlatitudes. It is therefore a good site to study the impact of such human presence on adjacent marine ecosystems. The objective of this data set was to enable the development and calibration of hydrodynamic and biogeochemical models of the bay, which was hindered by scarce knowledge of the environmental conditions. Water properties were collected using a Seabird Electronics SBE19plus and a Sontek CastAway CTD probe. Currents were measured using a towed acoustic Doppler current profiler (ADCP) model Teledyne RDI Sentinel V, and passive surface drifters which used Spot GPS probes.