This dataset presents dissolved oxygen (O2) concentrations, temperature and salinity profiles with water depths at 61 stations in the Kiel Bight, collected during the research cruises BE10/2018 (23.10.2018), BE03/2019 (15.03.2019), L23-13 (13.09.2023 - 15.09.2023), Hai24VE2 (24.09.2024), and EMB374 (04.09.2025 - 13.09.2025). The data were measured using dissolved oxygen, temperature and conductivity sensors (Sea-Bird, SBE43) attached to a stainless-steel framework. Temperature and salinity data are used to identify stratification patterns within the water column. Together with the O2 measurements, these data are used to characterize the seasonal development of hypoxia in the deep waters of the Kiel Bight. This understanding of hypoxic conditions is then combined with sediment and porewater data to identify controlling factors governing the accumulation of H2S at the Kiel Bight seafloor.