Nautilus is also a unique marine mollusk in China, belonging to the ranks of national first-class protected animals. According to the biological classification, Nautilus belongs to mollusca and Cephalopoda, and a subclass of Nautilus has been specially listed. However, although classified as a subclass, there are not many Nautilidae, including 1 order, 1 family, 2 genera and 6 species.

Nautilus, as a cephalopod mollusk, is a typical benthic animal. Generally speaking, they all live at the bottom of the water with a water depth of 100 meters, preferably in areas with seabed rocks or coral reefs. Because in these areas, they can attach to coral reefs through the secretions of their wrists.

Of course, Nautilus won't stay at the bottom of the sea all the time. In a calm situation, they will also float to the surface. Although these goods don't have any athletic ability, their body structure is very delicate, and they can float or sink by draining or absorbing water. It is through this characteristic of Nautilus that scientists have developed submarines.

/kloc-in the 0 th and 6 th centuries, real submarines appeared. 1578, the British mathematician William Bourne wrote the book Invention and Design to describe submarines. 1620, the first recorded "diving boat" was built by Cornelius Jabs Dyball, a Dutch-born Englishman, mainly according to the former design, and the propulsion was generated by manually operated paddles.

However, some people think that it is just "a bell-shaped thing tied under a surface ship" and is not a submarine at all.

From 1620 to 1624, it has two improved models for experiments on the Thames. In 2002, the BBC TV program "Building Impossible" was broadcast. Mark Edwards of Kyle built a Derbord submarine with two people on board according to the design drawings of that year, and successfully snorkelled in Doni Lake of Eton College.

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1648, John Wilkins, Bishop of Chester, wrote the book Mathematical Magic, which pointed out the advantages of submarines in military strategy:

1. Privacy: Go near any coast in the world without being discovered or suppressed.

2. Safety: Pirates and robbers cannot rob underwater ships; Unstable tides and strong wind and rain cannot affect 25-30 feet (5-6 steps) below the sea surface; Ice and frost can't endanger submarine crew, even in the Arctic and Antarctic waters.

3. Effectively resist the enemy navy, destroy and sink surface ships.

4. Support places surrounded by or close to water, and deliver materials silently.

5. As a useful underwater proving ground.

The first submarine used for military purposes appeared in the American War of Independence. David bushnell of Yale University built this turtle. By injecting water into the water tank through the pedal valve, the ship can dive 6 meters underwater and stay underwater for about 30 minutes. The boat is equipped with two hand-operated propellers, which enables the boat to achieve a speed of about 3 knots and control the boat's lifting.

There is a manual pressure pump in the boat, which can drain the water from the water tank and make the boat float. An explosive charge that can be detonated by a timing fuse is carried outside the boat and can be placed at the bottom of the enemy ship inside the boat. Only one person can operate the rudder and propeller inside.

1776, the turtle tried to attack HMS Eagle without success, but this was the first attempt by a submarine to attack a warship.

The first submarine that successfully sank an enemy ship in history was during the American Civil War. Horace Lawson Henley built the submarine "Henley", with eight crew members and driven by cranks. The explosive extends from its front end and explodes when it touches an enemy ship.

1864 February 17 at 9: 00 pm, the USS Housatonic frigate was successfully sunk, but it was also sunk due to the vortex generated by the explosion.

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