This paper discusses technology solutions that may be used to mitigate potential threats and security risks arising from small vessels operating in a busy urban maritime domain such as the New York / New Jersey maritime domain. The solutions focus on persistent surveillance by detecting, tracking, and classifying small vessels, and address the risk posed by these vessels. In a series of experiments conducted in the Hudson River, we collected and analyzed data from various sensors and evaluated several potential technology solutions for detecting these security threats. The threats are addressed across multiple scenarios, ranging from man-made threats to coastal hazards, using assets including radars; acoustic and infrared sensors; vessels and vehicles; and oceanographic and meteorologic prediction tools focused on the water surface, underwater, and urban environments. The results of our experiments show that the combination of sensors provides a valuable means to identify small vessels that may pose a threat in a busy harbor.