In water electrolysers, gas crossover caused by elevated dissolved gas concentrations poses a major challenge, reducing product purity, safety, and operational stability. However, most existing electrolyser models assume that all generated products leave the electrode in the gaseous phase, neglecting the dynamics of dissolved gas transport. Experimental observations from the literature reveal that bubbles can continue to grow even after detachment, suggesting significant dissolved gas supersaturation. In this work, we develop a computational multiphase flow model that couples the transport of dissolved gas, gas fraction, and volumetric interfacial area to quantify bubble growth within electrogenerated plumes. The model is validated using experimental data extracted from literature videos, where individual bubbles are tracked to determine their size and position over time. The absolute average relative error in predicting bubble diameters is below 7%, demonstrating the model’s accuracy. Results show that at a gas-evolution efficiency of 40%, detached bubbles can grow up to 1.4 times their initial diameter, corresponding to a threefold increase in volume. This confirms that the observed post-detachment bubble growth can be quantitatively explained by the uptake of dissolved gas within the plume. By incorporating this mechanism, the model enables improved prediction of dissolved gas distributions, supporting more reliable design and operation of industrial electrolysers.