The Associated Press was given a demonstration today in the Brooklyn Navy Yard of one corner of the waterfalls that will eventually be used for the National September 11 Memorial & Museum. The waterfall is part of "Reflecting Absence," designed by memorial architect Michael Arad. Builders have been tinkering with the project, which consists of two waterfalls and their pools, in anticipation of moving it to the Twin Towers site by the tenth anniversary of the attacks next year.