A submarine is a watercraft capable of independent operation underwater. It differs from a submersible, which has more limited underwater capability. Submarines have one of the widest ranges of types and capabilities of any vessel. They range from small autonomous examples and one or two-person vessels that operate for a few hours, to vessels that can remain submerged for six months. Here are some interesting facts about submarines.
1) Submarines are used by the military as part of navy forces, protecting aircraft carriers, performing reconnaissance and carrying out other tasks.
2) Some submarines can remain submerged for months at a time.
3) The first successful submarine was built in 1620 by Cornelius Jacobszoon Drebbel, a Dutchman in the service of James I of England.
4) USS Pennsylvania, a United States Navy Ohio-class ballistic missile submarine which has been in commission since 1989 is the largest nuclear submarine in the U.S. Navy.
5) Submarines are painted black for the same reason soldiers in Iraq wear desert camouflage. Underwater, a black submarine blends in with surroundings to help avoid enemy detection.