Simple solutions are quite often the best. I do not see a problem with this as it does make perfect sense. Oil floats but is not a solid and hay is a very textured solid that would affix itself to oil pretty strongly (think getting oil on your hands vs on a pane of glass).
From what I read somewhere (I think it was posted here, but I can't find it at the moment), a large amount of the oil is suspended in the water beneath the surface.
Huh? I can't find that anywhere. I can only find that it's traveling beneath the booms put in place to contain the oil (probably due to waves/volume).
Oil is low density and by nature floats. Oil is non-polar while water is polar (so they naturally separate). This isn't some magical oil spill - it has the same rules as pouring vegetable oil into a glass of water and stirring it.
I'm interested in what could cause oil to be suspended beneath something more dense (water). Perhaps it is just taking longer to reach the surface due to currents?
Well, it's not like it's going to go straight up. Keep in mind that if you pour vegetable oil into water and stir it vigorously enough, some of it will go beneath the water (admittedly, it won't dissolve into it or anything, it'll remain in big globules). A lot of oil is below the surface due to the sheer volume coming out (and yes, currents carrying it around :)).
