That’s what that “dispersant” is supposed to do- make the oil clump up and float a little below the surface for a more aesthetic oil disaster.
No, a dispersant's job is to break the oil into tiny micro-droplets that float to the surface.
It's really a surfactant, but surfactants cause dispersion because the ends of the surfactant molecules sticking out of the oil droplet repel the surfactant molecules in other oil droplets.
I caught triple-heck one evening here when I said that Corexit was nothing more than a glorified detergent. Folks told me that it was a dangerous poison and that Corexit was going to evaporate, fall out as rain, and contaminate the countryside.
I didn't have the heart to tell them about my education and job experience. I can't even begin to remember how many times I've designed and implemented bio-remediation projects for soil and groundwater contaminated with petroleum products. There are three things you need: Plenty of aeration, a bit of nutrients, and a good surfactant. Most engineers use Dawn detergent, which is simply a good, non-toxic surfactant.