Yes, they are real.
Yes, submarines are real vessels designed for underwater operations. They are used by navies around the world for various purposes, including military defense, research, and exploration. Submarines can operate at great depths and are equipped with advanced technology for navigation, communication, and combat.
They are very real.
The marines do not use submarines. Only the Navy does.
german submarines
german submarines
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Submarines are used both for military and rersearch purposes.
military submarines use low frequency antenna that extends from the sail(conning tower.) The message is typed into a computer, then is sent to another submarines antenna that receives it and displays it on a computer.
the military and navy use it for war and combat. Many submarines are made for launching missels and taking down ships and other subs.
Civilian-Under water research. Military-Stealth
Francis C. Malko
As regards military submarines meant as warships, the Russians built the submarines with the deepest diving capability, but U.S. submarines generally make less noise.