This dataset contains aggregated CTD (conductivity, temperature, depth probe) data corresponding to bottle closures for water sampling for stations conducted during the cruise SO301. Additionally it contains the corresponding helium isotope ratio measured in the lab post-cruise. The stations were executed in December 2023 to detect possible hydrothermal plumes at the Kairei Vent Site at approximately -25° latitude and 69° longitude. The data was measured with a CTD rosette system and processed to correct sensor uncertainties and remove outliers. For every parameter the mean, standard deviation, minimum and maximum are given which are associated with the time interval of closing one sample bottle. Navigational data from the ships positioning system, custom processed data from two different oxidation reduction potential sensors and corresponding data from Miniature Autonomous Plume Recorders (MAPR) are included and matched with the bottle data based on timestamps.