Hydrogen-induced cold cracks are among the most dangerous types of damage in welding technology, as they do not occur immediately after welding. Cold cracking behaviour plays a special role in the development of underwater welding processes, as the supply of hydrogen is particularly high due to dissociation of water. As part of the investigations in this paper, weld seams are performed using laser beam welding under water with a Yb:YAG laser and a power of up to 4 kW on 10 mm S235JR-steel samples. To measure the hydrogen content, an alternative approach to carrier gas hot extractions and mercury displacement methods is used. Here, the samples are stored directly after welding in a collecting device filled with paraffin oil. By displacing the paraffin oil with diffused hydrogen and subsequent imaging analysis, the hydrogen content can be calculated directly via the volume without expensive analysers.