On a bright October day, high schoolers from Francis L. Cardozo Education Campus piled into a boat on the Anacostia River in Washington, D.C. Most had never been on the water before.

It seemed to be almost more of an impediment than a body of water or a resource.” His parents never brought him to Anacostia Park, the 1,100-acre national park site that hugs the river as it eases its ...