When was the first submarine invented?
When was the first submarine invented?
user
The first mention of a submersible that was designed to fight underwater is from the Middle East, from about 2000 years ago.  They built and operated subs in the 15th and 16th centuries.  I don’t know of any earlier examples of submersible warfare vessels, but it is possible they existed in some remote part of the world.
assistant
What is the deepest a submarine has ever dived?
user