An ROV is a remotely operated vehicle which is a robot that moves in response to commands given by a human operator or a computer from a distance. Rov's mainly consist of a frame, a control system, a propulsion system, a tether management system and some usually have an on board camera. ROV's have been used for the last thirty years. They have been doing tasks that divers can't, do to Economical and safety reasons.
A Submersible is a piece of machinery designed to do an underwater function. Submersible's and rov's are important to Marine biologists so they can study underwater creatures. Geologists can use them to find out more about the evolution of the Earth by studying the ocean floor. The ocean holds some minerals that are becoming scarce on the Earth's surface. If we can set up mining stations under the water it would also provide many jobs. Undersea manufacturing plants would be practical if located close to materials needed that are in the sea. Crops such as seaweed could be harvested to make animal food and could also be used for human diets.
Oil is running low on the Earths surface and many oil platforms are becoming more and more important. Already 30% of oil used comes from those platforms. In another few years it will become about 50%.The Military could use submersible and Rov's to locate and retrieve sunken pieces of bombs, ships, etc. that belong to them
Deep sea exploration is The investigation of physical, chemical and biological conditions at the bottom of the ocean floor. Deep sea exploration can be used in Scientific and commercial purposes.