A bead having an exterior surface which is at least partially coated with a material that under illumination and in the presence of air is capable of accelerating the oxidation of organic compounds floating on water. The coated bead is water floatable and has an equivalent diameter of less than about 2 mm, preferably on the order of 10-30 microns. These coated beads can be used to accelerate under illumination oxidation of a floating oil film (e.g. from an oil spill) by dispersing the coated beads in the film and allowing them to be exposed to solar illumination and oxygen.