The navy's vision requirements are that the naked eye vision of the right eye is higher than 4.6 and the naked eye vision of the left eye is higher than 4.5. The "Examination Standard for Candidates" stipulates: Article 35, the naked eye vision of the right eye is less than 4.6, and the naked eye vision of the left eye is less than 4.5, which is unqualified. The naked eye vision of any eye is less than 4.8, and a corrective vision test is needed.

Navy refers to all military organizations of a country's maritime military and national defense, including ships, personnel and naval institutions. The army fighting at sea is usually composed of surface warship units, submarine units, aviation units, marine corps, naval coast guard and various professional units.

The emergence and development of the navy has a long history. It takes warships or warships as the main line, from primitive and simple ancient warships to multi-system modern warships, from individual scattered technology to intensive and comprehensive technology, and has gone through a long process of thousands of years.