NOVELTY - The unit (1A) has a subsea liquid unit (1c) for counteracting deformation of external housing (1a). A subunit (3) is arranged inside the external housing, and includes a passive pressure compensator (1b) that reduces pressure difference between pressure inside subunit housing and pressure inside the external housing. The subunit includes an electronic or electric device that is arranged inside the subunit housing, a type of liquid e.g. water, that counteracts deformation of the subunit housing and an absorber that absorbs a pollutant in the subunit.    USE - Subsea unit for a subsea power system e.g. power transmission system or power distribution system (all claimed) such as HVDC/HVAC power transmission or distribution system, for a seabed for oil and gas industrial application and offshore power generation application e.g. wind energy generation application, tidal energy generation application, wave energy generation application and ocean current energy generation application.    ADVANTAGE - The absorber efficiently absorbs pollutant in the subunit such that the pollutant does not float around inside the subunit and cause damage to the electronic or electric device contained within the subunit or within the unit and an area of an internal surface to be coated with the absorber that corresponds to an area of an entire internal surface of a wall of the subunit housing to improve absorption capacity of the absorber, so that long term performance of the unit can be improved, while eliminating thick walls for an enclosure when relatively small pressure difference exists between inside and outside an containment. The liquid fills the entire interior space of the subunit so as to prevent occurrence of air gaps between the inside surface of the subunit housing and an internal component contained in the subunit and counteracts deformation of the subunit housing when the subunit is subjected to ambient subsea pressure higher than pressure that the subunit housing can withstand without deformation.    DESCRIPTION OF DRAWING(S) - The drawing shows a side view of a subsea unit for subsea installation.    External housing (1a)    Subsea unit (1A)    Passive pressure compensator (1b)    Subsea liquid unit (1c)    Subunit (3)