The bay—200 miles long, up to 30 miles wide, recipient of river water from six eastern states—is the nation's largest estuary. It wasn't just a protein factory, it was the protein factory, producing more seafood per acre than any other body of water on earth. Hauls of oysters in the millions of bushels were common into the 20th century. It is estimated that in pre-colonial times there were enough oysters present to filter all the water in the bay every 3.3 days. By 1980, the same task took 325 days. In the 1970s, the bay was found to contain one of the earth's first marine dead zones—waters so depleted of oxygen that they can't support life. Masses of oxygen-starved crabs would, and still occasionally do, crawl ashore to breathe air, a behavior known by the macabre term crab jubilee.