This paper will be focus in contaminated seawater treatment and in a new technique, known as Plasma Assisted Processing, which was used to treat such seawater. This process is based on using cold plasma technology whereby radicals in the solution will reduce the chemical oxygen demand of the organic load. Herein the project explored the effectiveness of such plasma processing for polluted brackish or seawaters. In particular the project was focussed on water which has been contaminated with crude oils which could not be treated using conventional means. A first comparison between plasma treatment and Fenton process was carried out with water contaminated with phenol. It was observed that plasma process was more efficient (analysing the resources used and the removal obtained) than Fenton process. The efficiency of COD removal for plasma treatment was ~70-80%. It was also observed that there was no seawater influence in the plasma process. A second comparison between plasma treatment and Fenton process was carried out with water contaminated with crude oil. In this case, it was observed that there was seawater influence due to the COD removal obtained for seawater was 15% and for deionized water (sodium chloride 0.9%) was 25%. It was also observed that after 20 seconds plasma discharge the COD removal remains almost constant.