The earliest recorded submarine concept in the world was put forward by Italian Leonard. In A.D. 1500, he put forward the theory of "underwater navigation hull structure". 1578, British William Bourne published a book about submarines-invention. 1620, Dutch physicist KoNillies Derel successfully built a submersible, which is the first "ship" in human history that can dive and sail underwater. Its hull is like a wooden cabinet, with a wooden structure, covered with greasy cowhide and equipped with sheepskin as a ballast tank. This submersible ship is driven by multiple wooden paddles, can carry 12 crew members, and can dive 3-5 meters underwater. Derel's submarine is regarded as the prototype of submarine, so it is called "the father of submarine". The submarine first entered the war stage in 1776, during the American Revolution. At that time, David bushnell, a Yale graduate with patriotic enthusiasm, with the support of General Washington, began to study the method of attacking British troops with submersibles, and the famous "turtle" boat in the history of submarine development was born. "Turtle" boat looks like a turtle, and the air in the boat can be used for the driver to breathe for half an hour; The upper part of the hull is also equipped with two snorkels, which are open when floating and closed when diving to replenish fresh air for the submarine. In order to control the submarine's floating and sinking, there is a ballast tank in the boat, and the water in the tank is controlled by a hand pump. In order to cope with the emergency, the ship was equipped with 90 kilograms of iron blocks. If the iron block is thrown away in an emergency, the submarine can float quickly. The movement of "Turtle" is controlled by two propellers in horizontal and vertical directions driven by manpower. The weapon is a bomb bag weighing about 68 kilograms hanging outside the hull, which should be hung on the shell of the enemy ship when attacking.