ON 11 SEPTEMBER 2001, while the first formal emergency responders were trying to cope with the devastation caused by the attacks on the World Trade Center in New York City, an important–but rarely discussed – response activity was underway. In addition to the many people who evacuated Lower Manhattan by walking uptown or across the Brooklyn Bridge, an estimated 300,000 to 1,000,000 commuters and area residents were evacuated via an emergent flotilla of harbor vessels, including ferry boats, dinner cruise vessels, harbor tugs, and private watercraft. Some vessel captains followed directions issued by the US Coast Guard, whose officers had issued a call for all available boats to provide assistance. Other vessels converged to the site prior to, or without having heard, the Coast Guard call, and many acted independently and according to their best judgment, rather than under agency or harbor pilot direction. Quickly, a landward support network developed along the waterfront, with individuals taking steps to facilitate the embarking and disembarking of evacuees (either by providing direction, forming queues of evacuees, or removing barriers); providing basic first aid; transporting evacuees after they reached the waterfronts of New Jersey, Brooklyn, or Staten Island; or managing supplies, equipment, and emergency personnel to be transported back to the event site (Ground Zero). Although no pre-existing plan outlined the way in which this activity evolved, the waterborne evacuation was improvised successfully and illustrates the important role that citizens and non-governmental organizations play in emergency evacuations and disaster response efforts.