Underwater vehicles with on-board manipulators present a cost-effective technological solution to problems in oceanic exploration. This paper presents a comprehensive review of the underwater robotics literature, with special emphasis on remotely operated vehicles and autonomous underwater vehicles with on-board manipulators which enable underwater monitoring and intervention. Key issues in the operation and systems integration of underwater vehicle-manipulator systems, problems of coordinated control, and sensor-based navigation are discussed. Emerging trends in the field of underwater robotics are highlighted.