The CO2 Gas Sensor is a Gas sensor. You will ruin the sensor if it is placed in water or other solutions. Do not place any of our CO2 Gas Sensors into water or solutions.
To measure dissolved CO2s in water or other fluids, you need a dissolved CO2 sensor. Dissolved CO2 sensors are typically very sensitive to pH changes, as a result, to measure dCO2 accurately you need to use an appropriate buffer, which makes the use of this type of probe less than ideal for field work.