Some numbers to think about.

One oil barrel holds 42 gallons of oil.  That's 168 quarts of oil.

One quart of oil can contaminate up to 250,000 gallons of water.  So one barrel of oil has the potential to contaminate about 42 million gallons of water.

On June 3, 2010 USA Today quote the BP Oil Leak at 800,000 gallons of oil a day , or 19,048 barrels per day.  That's enough oil to fill a supertanker in about 105 days or 3 and a half months.  Just FYI a typical supertanker hold 2 million barrels of oil (84 million gallons).   The current estimate as of June 15, 2010  according to the Washington Post say the oil leak surges between 30,000 and 60,000 barrels per day.  Ok, let's put on our thinking caps shall we.

Let's say the average flow is 45,000 barrels a day, and BP can recover 18,000 barrels.  That's still 27,000 barrels each day leaking into the Gulf of Mexico.  To be fair BP does say that it's recovery rate will increase by mid-July to the point where they capture all the oil.  So just for a back of the envelope calculation let's say 27,000 barrels a day is the total leak over the whole time period.  That takes care of the underestimate early on and the improving oil recovery until the end of the crisis.  This leak started with the demise of the Deep Water Horizon Oil rig on April 20, 2010.  Assuming the leak can be stopped or at least by mid-July (July 16) that is 87 days.

27,000 barrels a day for 87 days is 2,349,000 barrels of oil.  That's a supertanker and a little friend as well.

OR IN OTHER WORDS

2.35 million barrels of oil can contaminate up to 98.6 trillion gallons of water.  How much is that?   I'm glad you asked.  :)

The Gulf of Mexico holds about 650 Quadrillion Gallons of water.  Look at the amount of possible contaminated water compared with the Gulf of Mexico that's about 0.0151% of the total water in the Gulf.  That doesn't sound like much, but all that oil has to somewhere.  Most of it will wash up in the Photic layer of the ocean and then end up on the shore.  The rest will settle into the silt when the clam, oysters and bottom feeders are.  Only the truly lightest hydrocarbons will evaporate.  Any way you cut it, a night out at Red Lobster is going to be a lot more expensive.