Humans have been interested to the sea since long time ago. The more technologies are available as the time passes, the more curiosities develop: what is in the deep ocean? Many people have tried to challenge to this question, but in this paper I focus only on the scientific viewpoint. In order to solve the question above, scientists have developed a lot of methods to go to the deep ocean, deeper and wider. Some examples are the submarines, submersibles, satellite systems, autonomous underwater vehicles (AUV), or remotely operated vehicles (ROVs). Submarines can go really deep but its ability restrict to mostly army forces. Also, due to its largeness and hardness to drive, it would be difficult to use for the scientific observations. From the geographical point, the satellite systems are really useful and actually in operation currently. It is, however, almost impossible to see what in the ocean and how marine animals move or marine plants disperse. AUV and ROVs are recently developed technologies to investigate the deep ocean. Those machines are relatively small and have great movabilities in the ocean, and we can check how does the deep ocean look like through the water camera that is attached to the vehicles. It sounds that this is the best way to investigate the deep world, but even after the development of convenient and safer unmanned operated vehicles, we still eager to see the real ocean basin with our eyes. Why? There must be something that we cannot learn through the mechanical camera. Or more simply, we just want to see it!! Therefore, thorough this paper, I will talk about how the manned operated vehicles (MOV), or deep submergence vehicle (DSV), historically developed, what is important and what would do in the future. .
Compared to the submarines, submersibles are really small but can go greater depth because of its size. In old period, humans tried to go deeper by several kinds of ways such as the diving bell or diving helmet (1).