In round figures, let's say 12 million gallons of oil have spilled since the Deepwater Horizon platform sank on April 24 (that assumes 200,000 gallons a day for 60 days).
The Gulf of Mexico contains 660 quadrillion gallons of water.
Imagine that the Gulf were the size of an Olympic-sized swimming pool (which contains about 660,000 gallons of water). On that scale, how much oil do you think has been spilled so far? About a bucket? Nope. Maybe a cup? Not even close. Perhaps a thimble? Much less even than that.
The correct figure is a volume equal to 1/14 of a single M&M candy. You can do the math yourself and verify this.
Of course, the effect will be magnified as the oil arrives on the beaches - it will be concentrated from a diffuse cloud in the ocean to the surf line. But we're still talking about an incredibly small amount of oil here. Something to bear in mind.