a noun it generally refers to a vessel that can travel underwater. The term is a contraction of submarine boat. and occurs as such in several languages, e.g. French (), and Spanish (), although others retain the original term, such as Dutch (), German (), Swedish (), and Russian (: ), all of which mean 'submarine boat'. By naval tradition, submarines are still usually referred to as boats rather than as ships, regardless of their size. Although referred to informally as boats, U.S. submarines employ the designation USS (United States Ship) at the beginning of their names, such as . In the Royal Navy, the designation HMS can refer to "His Majesty's Ship" or "His Majesty's Submarine", though the latter is sometimes rendered "HMS/m" and submarines are generally referred to as boats rather than ships. Early human-powered submersibles 16th and 17th centuries According to a report in Opusculum Taisnieri published in 1562: In 1578, the English mathematician William Bourne recorded in his book Inventions or Devises one of the first plans for an underwater navigation vehicle. A few years later the Scottish mathematician and theologian John Napier wrote in his Secret Inventions (1596) that "These inventions besides devises of sayling under water with divers, other devises and strategems for harming of the enemyes by the Grace of God and worke of expert Craftsmen I hope to perform." It's unclear whether he ever carried out his idea. Jerónimo de Ayanz y Beaumont (1553-1613) created detailed designs for two types of air-renovated submersible vehicles. They were equipped with oars, autonomous floating snorkels worked by inner pumps, portholes and gloves used for the crew to manipulate underwater objects. Ayanaz planned to use them for warfare, using them to approach enemy ships undetected and set up timed gunpowder charges on their hulls. The first submersible of whose construction there exists reliable information was designed and built in 1620 by Cornelis Drebbel, a Dutchman in the service of James I of England. It was propelled by means of oars. 18th century By the mid-18th century, over a dozen patents for submarines/submersible boats had been granted in England. In 1747, Nathaniel Symons patented and built the first known working example of the use of a ballast tank for submersion. His design used leather bags that could fill with water to submerge the craft. A mechanism was used to twist the water out of the bags and