Before you is the life story of our compatriot, a sailor and patriot, a scientist and a naval commander, who from childhood connected his life with the Great Transformer of Russia and the favorite brainchild of Peter the Russian Fleet. Having passed the selection to the Navigation School, having received basic knowledge and practice of sailing, he was sent for training in the French Navy, where he completed a full course of training from a naval midshipman to the officer rank of naval second lieutenant. Then, with his whole life and service, he proved Peter’s correct choice and his devotion to the Motherland. Semyon Mordvinov left behind scientific works on navigation and organization of naval affairs. Compiled and finalized tables of ship signals. On duty, he sorted out and systematized documents on the organization of the fleet left after Admiral Apraksin. Thus laying the foundation for the Russian Naval Archive. His name and deeds are undeservedly forgotten by his descendants.