An in-liquid state of a mobile device is detected by processing color components indicative of an intensity of the ambient light at different wavelengths and a pressure data indicative of ambient pressure. A first plausibility index indicates a likelihood of an air/liquid transition as a function of variations of at least two color components. A second plausibility index indicates a likelihood of an air/liquid transition as a function of variations of said ambient pressure. If both the first and the second plausibility indices indicate a likely air/liquid transition event, an in-liquid state signal is generated.