Underway sensors data collected during Maria S. Merian cruise MSM130 ('Polar Beast') in July-August 2024 across the southeast Greenland shelf and three fjord systems. Measurements include ship-specific data, hydrological data and meteorological data downloaded from the Merian DSHIP system at 1 min resolution. An additional sensor suite was immersed into an onboard water tank supplied with seawater from approximately 6.5 m. The suite of sensors included a multiparameter EXO1 Sonde for measurements of temperature, salinity and dissolved oxygen, a VLux AlgaePro fluorometer for chlorophyll a and b, an Opus nitrate sensor, two sensors – SAMI and AquapHOx-L - for colorimetric and optical measurements of pH, respectively and an HydroC sensor for pCO2 measurements. The EXO1 oxygen probe was calibrated prior to the cruise using one-point air saturated water. The temperature offset compared to ship temperature is due to the warming up of the seawater flowing through the pipelines from the seawater inlet to the onboard water tank. Chlorophyll a and b data from Vlux are reported corrected according to manufacturer calibration. Nitrate data from OPUS sensor were processed according to Nehir et al, 2021. An offset of 6 µM was applied based on spectrophotometric measured nitrate concentrations on discrete water samples. pH data from AquapHOx sensor were processed using Pyro WorkBench software. A 3 point calibration was performed prior to deployment using custom-made pH buffer solutions. Details on data processing procedures can be found in Staudinger et al., 2018. Raw absorbance data from SAMI-pH were corrected for sample salinity and converted to pH (total scale) using QC_pH standalone Matlab program. Details on data processing procedures can be found in Liu et al., 2011. Meta-cresol purple (mCP) used in the SAMI sensor was purified according to Liu et al, 2011. Mole fraction CO2 data from the HydroC sensor were processed according to Fietzek et al, 2014 to account for the pressure behind the membrane in the sensor's gas stream and converted to in-situ pCO2 (in µatm) according to Takahashi et al., 1993.