Real-time underwater visualization has been extremely slow to develop within the offshore industry and has generally been limited to 2D representations of vessel positions on digital charts. Only recently have marine industries realized the potential of 3D real-time virtual environments and visualization systems for effective management planning and real-time situation awareness. We describe a real-time visualization of the clean-up of a former US Naval Submarine Base, located in Holy Loch, Scotland. Our Whole-Field Modeling System has provided an accurate real-time visualization of numerous varying parameters such as remotely operated vehicles (ROVs), cranes, barges, grabs, magnets, and detailed seabed topography. The system improved the field staffs' spatial and temporal awareness and facilitated decision making within the complex offshore working environment. A side bar discusses another application, offshore diamond mining.