Submarine

A submarine is a type of vessel that can move below the surface of the sea and stay underwater for long periods of time. The word submarine comes from Latin words meaning "under the sea." Unlike ordinary ships, which float on the surface, submarines are built to dive, travel, and return safely to the surface. They are made with strong materials so they can withstand high water pressure at great depths.

Submarines control their depth using tanks called ballast tanks. These tanks can be filled with air or water. When the tanks fill with water, the submarine becomes heavier and sinks. When water is pushed out and replaced with air, the submarine becomes lighter and rises. This system allows careful control of movement up and down in the ocean. The shape of a submarine is smooth and rounded to help it move easily through water.

Early submarines were small and could only stay underwater for a short time. One early example was built by Cornelis Drebbel in the early 1600s. Modern submarines developed mainly in the 20th century. During World War I and World War II, submarines were widely used by navies. Germany used submarines called U-boats, which attacked ships from below the surface.

Modern submarines use different power systems. Some use diesel engines and batteries. Others use nuclear power, which means energy produced by controlled nuclear reactions. Nuclear-powered submarines can stay underwater for months because they do not need air for their engines. They carry food and supplies for long missions and can travel very far without surfacing.

Submarines are also used for science and exploration. Research submarines study ocean life, map the sea floor, and explore deep areas where humans cannot dive. Some submarines are designed to carry cameras and robotic arms. These tools help scientists collect samples and observe underwater environments.

Life inside a submarine is limited by space. Crew members work, sleep, and eat in tight areas. Air, water, and power must be carefully managed. Despite these limits, submarines remain important tools for underwater travel, defense, and research, because they can reach places that surface ships cannot.