Its a streamlined beast that crawls beneath the water surface with stealth. its designed for the military but some are made recreational. It can float to the water surface due to displacement lift leading to bouyancy i.e the weight of water it displaces is equal to the weight of the ship causing lift. A submarine cross section is comprised of a inner hull, outer hull, ballast tanks, two vents and an opening. When the submarine is at the surface ballast tanks are filled with air and the vents are closed thus rendering the submarine less denser than the surrounding water keeping it floating. in case the submarine wants to sub merge, the vents are open and the ballast tanks are filled with water making the submarine more denser than the surrounding water. consecutively the air in the ballast tanks is pushed out by pumps.
Compressed air is supplied in the submarine in air flasks for life support and use in ballast tanks.
hydroplanes at the stern help to control the angle of the dive. They are angled so that water moves over the stern. This forces the stern upward therefore the submarine is angled downward. there are also trim tanks at the back which work together with ballast tanks.
most submarines well except nuclear ones have diesel electric engines this is due to limited supply of air inside the water. they work almost like a hybrid car. The engine drives a generator that charges the battery that drives the motor which rotates the propeller. it should be noted that the diesel engine is mostly used when the sub is near the water surface, when its below the stored charge drives the submarine. The nuclear submarines use nuclear power which harnesses energy from nuclear reactors containing uranium e.t.c to produce power to propel the submarine. This can be used either near the surface of submerged deep in the waters.
At the center of the submarine just below the sail better known as the conning tower houses the navigation and equipment. a periscope is used when near the surface for peeping i.e without causing attention especially for battle purposes. A submarine also uses GPS satellite to tell position, sonar which resembles radar which sends out pulses of sound at sea and listens for echoes reflecting i.e from other submarines e.t.c. inertial guidance is also used, it used gyroscopes to track of how far the submarine has traveled and for how long.
life support is available in the submarine i.e electricity is made by a generator. water i.e H20 is broken into h2 and 02 by electrolysis whereby clean air is produced for human inhalation. salt is removed from salty water to produce clean water for human consumption. Trash is compacted into steel cans and disposed in the water.