Leonardo da Vinci sketched a submarine for covert naval attacks.
His notes describe an underwater vessel intended to approach enemy ships without being seen. The concept belongs to his studies of military engineering and naval warfare, where concealment could provide a tactical advantage.
Leonardo’s submarine was not a modern powered submarine. The surviving descriptions do not provide a complete, practical propulsion and life-support system comparable to later submarines, and no reliable evidence shows that he built or tested one.
Some accounts say Leonardo withheld or concealed details because he feared that underwater warfare could be used destructively. Whether that interpretation is literal or speculative, the sketch demonstrates his early interest in controlled underwater navigation.