The AUV (Autonomous Underwater Vehicle) is not restricted by the umbilical cable and able to swim freely. Complex control is, however, significantly difficult, because of low rate and long delay in acoustic link between the operators and the vehicle. Since there are many complicated missions for underwater vehicle which need powerful operators control ability, it is desirable that unmanned untethered underwater robots in deep water could be remotely controlled by the operators on surface. In this paper, the teleoperation system for unmanned untethered underwater robots, which cope with long time delay of acoustic communication, is proposed. A virtual robot which should immediately represents the result of remote control is simulated and shown to the operators on the graphical workstation as prediction computer graphics. Both the virtual robot and the real robot have the same "World Model" which has been constructed based on predetermined configuration of the seabed and obstacles. These robots generate their path and move themselves by receiving intermittently operators' commands. The real robot status and the information on encountering with unknown obstacles, which has not been written in the World Model, are sent to the workstation. The operators can decide how to operate the vehicle in support with three-dimensional computer graphics (3 DCG) on the workstation, which compares the motion of the virtual robot and that of the real robot in the World Model. The workstation provides the whale view and the virtual diver view to back up the operation. The proposed system is evaluated by the simulation experiments, and the results show that long delay in acoustic communication can be overcome and that remotely operation can be realized by the proposed system.