Cavalier India Defence Training Academy

A submarine (or sub) is a watercraft capable of independent operation underwater. It differs from a submersible, which has more limited underwater capability. It is also sometimes used historically or colloquially to refer to remotely operated vehicles and robots, as well as medium-sized or smaller vessels, such as the midget submarine and the wet sub. Submarines are referred to as "boats" rather than "ships" irrespective of their  What is a submarine? Oceans are most turbulent where wind meets water: on their surface. The waves that race across the sea are a sign of energy, originally transmitted by the Sun and whipped up into winds, racing from one side of the planet to the other. Ships battle and lurch across tough seas where no fish—worth its salt—would ever swim. Sailing ships make good use of winds, harnessing the gusts of air to make a very effective form of propulsion. Diesel-powered ships stay on the surface for a different reason: their engines need a stea...