Thermal conductivity data of coastal sediments were collected during the ALKOR cruise AL591 in April 2023 using the "classic" HeatFlowProbe, where the penetration into the sediment was driven solely by the weight of the probe. The system uses a sensor string that contains 22 thermistors (NTCs) and a heating wire over which a defined heat pulse is released. In-situ temperature and thermal conductivity of the sediment are calculated for each thermistor using the inversion method according to Hartmann & Villinger (2002).