The CONTROS HydroC® CO 2 sensor is a unique and versatile underwater carbon dioxide sensor for in-situ and online measurements of dissolved CO2. The CONTROS HydroC® CO2 is designed to be used on different platforms following different deployment schemes. Examples are moving platform installations, such as ROV/ AUV, long term deployments on seabed observatories, buoys and moorings as well as profiling applications using water sampling rosettes.