The creation of the world's first underwater minelayer "Crab" is one of the remarkable pages in the history of Russian military shipbuilding. The technical backwardness of tsarist Russia and a completely new type of submarine, such as the Crab, led to the fact that this mine layer entered service only in 1915. But even in such a technically developed country as Kaiser Germany, the first underwater mine layers appeared only in the same year, and in their tactical and technical data they were significantly inferior to the Crab.