ABSTRACT Pumping viscous oil, whether when lightening a disabled vessel or recovering spilled oil, has always been an obstacle to efficient operations aiming to avoid or limit the impact of an oil spill. French authorities have had to deal with this during many oil spills: for example, the Amoco Cadiz, Tanio, or, more recently, the Amazzone incident. For many years, CEDRE and Institut Français du Pétrole (IFP) have been developing and testing various methods of improving the handling of naturally viscous products like heavy fuels or products that have become viscous by the formation of a water-in-oil emulsion. The technique of injecting a ring of water at the periphery of the hoses was studied. After some preliminary tests done by IFP on a laboratory scale, full-scale experiments were conducted by CEDRE using a specially designed injector. This device enabled a large reduction of the pressure drop in the back flow of a volumetric pump moving heavy fuels. The influence of different parameters also was evaluated. Concerning a break-up of “chocolate mousse” emulsions, it was necessary to verify the effectiveness of demulsifiers when applying them in the presence of free water, such as found when actually recovering oil spilled at sea. The influence of different parameters was first studied with a laboratory physical model and then confirmed during full-scale tests.