What is a submarine ? How can it be made to dive in water and come to the surface of water?

A submarine is a watercraft capable of operating underwater. It is designed to navigate and travel beneath the water surface for extended periods. Submarines are used for various purposes, including military operations, scientific research, exploration, and rescue missions.

How submarines dive and surface:

Buoyancy and Ballast Tanks: Submarines use the principle of buoyancy to control their depth in the water. When a submarine wants to dive, it fills ballast tanks with seawater. By doing so, the submarine becomes heavier than the water it displaces, causing it to submerge. To surface, the submarine releases the seawater from the ballast tanks, allowing it to become lighter and rise to the water's surface.

Main Ballast Tanks: Submarines have large, high-capacity tanks known as main ballast tanks. These tanks are located in the lower portion of the submarine's hull. By adjusting the amount of water in these tanks, the submarine can control its overall buoyancy, thus ascending or descending in the water.

Trim Tanks: In addition to the main ballast tanks, submarines may have smaller trim tanks located in various positions along the hull. These tanks allow the submarine to make fine adjustments to its angle while diving or surfacing, ensuring it maintains a stable position.

Propulsion and Control Surfaces: Submarines are equipped with propulsion systems, usually powered by electric motors or nuclear reactors. These propulsion systems drive the submarine's propellers, allowing it to move forward or backward. To control its direction, submarines use control surfaces, such as diving planes (located on the front of the sail) and rudders, which help the submarine to tilt or turn as needed.

Sail and Conning Tower: The sail is the raised structure on the top of the submarine that houses various equipment, periscopes, and access hatches. The conning tower is a part of the sail where the commanding officer may control the submarine while surfaced or partially surfaced.

Snorkel: When submerged, submarines need to access fresh air for the crew and the engines. They achieve this by using a snorkel—a retractable tube that extends above the water's surface, allowing the submarine to draw in air for ventilation and the engines while remaining mostly submerged.

By skillfully managing the water in the ballast tanks, adjusting the angles with the control surfaces, and using the propulsion system efficiently, submarines can safely and effectively dive and surface as required. It's important to note that modern submarines are incredibly sophisticated vessels with advanced technology, enabling them to operate underwater for extended periods and navigate in various conditions.