The Deepwater Horizon oil blowout in the Gulf of Mexico led to the largest offshore oil spill in U.S. history. Quantifying the actual oil volume of large oil slicks on the ocean surface has proven to be a challenge to researchers and responders alike, but this challenge must be addressed to assess and understand impacts on marine and coastal resources, and to prepare for future spills. Abt’s Jamie Holmes and his co-authors estimated surface oil volume using coarse-resolution optical remote sensing observations. The article won a best paper award from the Journal.