Book excerpt: It is innate in human being to discover and explore what they do not know and the ocean is one of those. The sea covers 71% of the earth's surface. We know the five great oceans are: Pacific, Atlantic, Indian, Arctic and Antarctic but we know only the 10% of the deep sea, and we know less than 10% of the creatures that live there. Definitely one of the factors that has played as an antagonist in the knowledge of the sea, was the absence of technologies to explore the depths. Fortunately in 60 years, man has made great strides, managing to get to touch even the deepest point of the abyss, the Mariana Trench and this is thanks to modern technology as ROV. The ROVs are used in scientific research, in the Oil & Gas, defense, research for humanitarian purposes, in the construction and maintenance of marine culture, such as support to renewable energy, nuclear, in archeology, in the hunt for treasures and openings of sea mines. Many people are wondering what ROVs are and what they are used for, others are wondering how to become a ‘ROV Operator’. The purpose of this manual is not only to give an answer to these questions but also to teach future ROV pilots how to become professionals marine robotics.