 French and German inventions followed closely, and the term "torpedo" came to describe self-propelled projectiles that traveled under or on water.By 1900, the term no longer included mines and booby-traps as the navies of the world added submarines, torpedo boats and torpedo boat destroyers to their fleets.Whitehead was unable to improve the machine substantially, since the clockwork motor, attached ropes, and surface attack mode all contributed to a slow and cumbersome weapon.