During research cruise MSM99/2 (26/03/2021-05/04/2021) eleven hydro-casts (SBE9plus-CTD measurements) were performed in two different working areas located north and south-east of Helgoland, North Sea. The main aim was to characterize the water column above a giant pockmark field north of Helgoland. For each CTD cast the following data were recorded:Time (UTC), latitude (°N), longitude (°W), water depth (m), pressure (db), temperature (°C), salinity, oxygen (µmol L-1), oxygen (sat., %), turbidity (FTU), sound velocity (Chen-Millero, m s-1), light intensity (PAR, µmol photons m-2 s-1), fluorescence (a.u.)