Current research on wireless sensor networks is based on the assumption that these networks are deployed in a terrestrial environment. Relevant protocols and design specifications are developed under this condition. This makes the deployment of currently existing wireless sensor networks in marine environments extremely challenging. We present major challenges and applications of underwater wireless sensor networks focusing on their military aspect. The paper addresses the army’s immediate needs for secure agile broadband communications for future digital battlefields emphasizing the role of marine sensors. A novel architecture for broadband ad hoc and sensor networks that can provide warfighters with a secure on-the-move means for high-capacity communications is proposed. The architecture is designed with the role of ad hoc and sensor networks in future warfare scenarios and anticipated demand for broadband applications.