This document is a classified field manual for Maritime Unit operations within the Office of Strategic Services (OSS) during World War II. It outlines the missions, methods, organization, planning, personnel, and training for Maritime Units. Their missions included clandestine ferrying, maritime sabotage, and providing military tactical assistance. The manual describes specialized equipment and techniques for underwater operations. It also details the organizational structure of Maritime Units within OSS branches and field bases and the planning process for operations.