1. Do you know the difference between a submarine and a submersible? A submarine is a watercraft that is capable of independent operation under the sea. Submarines do not require support ships because submarines can renew their air and power supplies independently. Submersibles also submerge and operate underwater, but they need the support of a larger vessel. Submersibles cannot renew their air and power supplies without support. For this reason, submersibles are usually smaller and cannot spend as much time underwater as submarines.

2. The first documented submersible was constructed in 1620 by Cornelius Drebbel. It was powered by rowing oars underwater. In 1648 Bishop John Wilkins wrote, “It may be of great advantages against a Navy of enemies, who by this may be undermined in the water and blown up.” Over one-hundred years later, the first military submarine was ready to be deployed.

3. The Turtle was the world’s first submarine used in combat. Designed by David Bushnell in 1775, it was deployed by the Continental Army during the American Revolutionary War.

4. Another notable submarine originally designed for war was Julius H. Kroehl’s Sub Marine Explorer. Built between 1863 and 1866, this submarine was created for the North during the American Civil War but the war ended before it went into use. After the war it was used commercially to harvest pearls in Panamanian waters during the late 1860s. Unfortunately, the dangers of decompression sickness (a condition that occurs when divers rise to the water’s surface too quickly) were not understood. While experimenting with the Sub Marine Explorer in 1867, Kroehl himself perished from decompression sickness. In 1869 a new engineer put the Sub Marine Explorer back to the task of harvesting pearls. Tragically, use of the Sub Marine Explorer was discontinued after the entire crew died from decompression sickness.

5. Submarine use increased greatly during World War I. Due to innovations in engineering, such as a dual power system using both diesel and electric sources, submarines had finally developed into effective war machines like the U-Boat.

6. Modern submarines are now powered by a nuclear reactor. The nuclear reactor generates a tremendous amount of power which allows submarines to operate at high speeds for long durations. The only factor limiting the amount of time that and advanced submarine can remain submerged is the amount of food and water that it can carry