SUBMARINES.

The first submarine was built in 1775 by the American David Bushnell, and it was used to sink an English ship towards New York borders, but it failed because it could not stay enough time under the water.

Nautilus submarine.

In 1801 Robert Felton the American has built a submarine for the French and called it Nautilus, it was sailing over the water surface by sails and runs under the water with a propeller that is tide to a transmitter of movement from 4 pedaling men. It was carrying enough oxygen and enough air for lighting two candles for about two hours.

Marine Turtle submarine.

Making a submarine work underwater remained a problem for a long time until the diesel engine was invented because the steam engines were not appropriate, furthermore the danger of explosion prevented them from using the Gasoline engines, during the ww2, great improvements were made to the submarines between the two fighting sides in order to sink each other supply ships with torpedos and submarines could stay underwater from 2 days to 3 days.

The Periscope.

The modern submarines work underwater with an electric engine that fed by a group of batteries, while diesel engine and submarine work over the water surface that is connected to the batteries for recharging purposes.
Only recently the nuclear power was used to run the submarines. the nuclear submarine is equipped with a small nuclear reactor that generates heat to make steam from water and uses the pushed stem to run a turbine which is connected to the submarine's fan.
The nuclear submarine has many advantages over fuel submarines, which includes a few nuclear fuel is needed and the sub is capable of disappearing underwater for months.

Tektite Underwater marine base.

The sir Hubert Wilkins the Australian, tried to reach the north pole in 1931 by sailing underwater with a regular submarine under the crusty ice, but he failed because he had to reach the surface many times asking for air supplies.
In 1958 the American navy fleet has returned to the north pole to retry passing under the icy crust with a nuclear submarine called "Nautilus" which was accompanied with three compasses especially designed to work in the north pole and remote sensors to measure the distance between the icy crust layer on the surface and the ocean bottom, finally, they could achieve the mission and return home safely.

Sir Hubert Wilkins.

A few types of research are now under conduction in order to make it possible for humans to live underwater and adapt with an enormous amount of oceanic pressure. a marine lab was designed over the Atlantic ocean with three scientists living within it near California beach to study human life underwater.