An in-line dual water scrubber for gas cleaning onboard a vessel, comprising a vertical extended body, a gas inlet, a gas outlet, - said gas inlet is underlying in said lower section of said extended body and said gas outlet is overlying in said upper section of said extended body, said gas inlet comprising a water trap, a first underlying scrubbing section comprising one or more first circuit liquid inlets, one or more first scrubbing liquid spray means one or more first circuit liquid outlets, for a first scrubbing liquid, a second scrubbing section in upper section of said extended body, comprising one or more second circuit liquid inlets, one or more second scrubbing liquid spray means one or more second circuit liquid outlets, for a second scrubbing liquid, - further said first scrubbing liquid connected to a first liquid handling system and said second scrubbing liquid is connected to a second scrubbing liquid handling system, said handling systems (40, 50) are outside the extended scrubber body, characterized by - said second handling system having a chemical adding equipment, said liquid handling systems (40, 50) arranged with switch means (41, 51) connected to said inlet (4i,5i) and said outlet (4o,5o), arranged for separate handling of said first and second scrubbing liquid (4l,5l) either in a closed loop (40c, 50c) or in an open loop (40o, 50o), wherein at least one of the scrubbing liquids (4l, 5l) is ambient water, generally sea water, - one ore more liquid collectors arranged above said one or more first scrubbing liquid spray means, said liquid collector arranged in fluid connection with said second circuit liquid outlets for collecting one or more said second scrubbing liquid and for flow through of a vertical upwards flowing gas-flow from said inlet to said outlet. - said gas inlet is underlying in said lower section of said extended body and said gas outlet is overlying in said upper section of said extended body, said gas inlet comprising a water trap, a first underlying scrubbing section comprising one or more first circuit liquid inlets, one or more first scrubbing liquid spray means one or more first circuit liquid outlets, for a first scrubbing liquid, a second scrubbing section in upper section of said extended body, comprising one or more second circuit liquid inlets, one or more second scrubbing liquid spray means one or more second circuit liquid outlets, for a second scrubbing liquid, - further said first scrubbing liquid connected to a first liquid handling system and said second scrubbing liquid is connected to a second scrubbing liquid handling system, said handling systems (40, 50) are outside the extended scrubber body, - said second handling system having a chemical adding equipment, said liquid handling systems (40, 50) arranged with switch means (41, 51) connected to said inlet (4i,5i) and said outlet (4o,5o), arranged for separate handling of said first and second scrubbing liquid (4l,5l) either in a closed loop (40c, 50c) or in an open loop (40o, 50o), wherein at least one of the scrubbing liquids (4l, 5l) is ambient water, generally sea water, - one ore more liquid collectors arranged above said one or more first scrubbing liquid spray means,