Naval warfare
The 3rd-century writer Zhang Yan asserted that the people of the Warring States period named the boats this way because halberd blades were actually fixed and attached to the hull of the ship in order to rip into the hull of another ship while ramming, to stab enemies in the water that had fallen overboard and were swimming, or simply to clear any possible dangerous marine animals in the path of the ship (since the ancient Chinese did believe in sea monsters; see Xu Fu for more info).
Qin Shi Huang, the first emperor of the Qin dynasty (221–207 BC), owed much of his success in unifying southern China to naval power, although an official navy was not yet established (see Medieval Asia section below). The people of the Zhou dynasty were known to use temporary pontoon bridges for general means of transportation, but it was during the Qin and Han dynasties that large permanent pontoon bridges were assembled and used in warfare (first written account of a pontoon bridge in the West being the oversight of the Greek Mandrocles of Samos in aiding a military campaign of Persian emperor Darius I over the Bosporus).
During the Han dynasty (202 BC–220 AD), the Chinese began using the stern-mounted steering rudder, and they also designed a new ship type, the junk. From the late Han dynasty to the Three Kingdoms period (220–280 AD), large naval battles such as the Battle of Red Cliffs marked the advancement of naval warfare in the East. In the latter engagement, the allied forces of Sun Quan and Liu Bei destroyed a large fleet commanded by Cao Cao in a fire-based naval attack.
In terms of seafaring abroad, arguably one of the first Chinese to sail into the Indian Ocean and to reach Sri Lanka and India by sea was the Buddhist monk Faxian in the early 5th century, although diplomatic ties and land trade to Persia and India were established during the earlier Han dynasty. However, Chinese naval maritime influence would penetrate into the Indian Ocean until the medieval period.

Early modern: The late Middle Ages saw the development of the cogs, caravels and carracks ships capable of surviving the tough conditions of the open ocean, with enough backup systems and crew expertise to make long voyages routine. In addition, they grew from 100 tons to 300 tons displacement, enough to carry cannon as armament and still have space for cargo. One of the largest ships of the time, the Great Harry, displaced over 1,500 tons.
The voyages of discovery were fundamentally commercial rather than military in nature, although the line was sometimes blurry in that a country's ruler was not above funding exploration for personal profit, nor was it a problem to use military power to enhance that profit. Later the lines gradually separated, in that the ruler's motivation in using the navy was to protect private enterprise so that they could pay more taxes.
Like the Egyptian Shia-Fatimids and Mamluks, the Sunni-Islamic Ottoman Empire centered in modern-day Turkey dominated the eastern Mediterranean Sea. The Ottomans built a powerful navy, rivaling the Italian city-state of Venice during the Ottoman–Venetian War (1499–1503).
Although they were sorely defeated in the Battle of Lepanto (1571) by the Holy League, the Ottomans soon rebuilt their naval strength, and afterwards successfully defended the island of Cyprus so that it would stay in Ottoman hands. However, with the concurrent Age of Discovery, Europe had far surpassed the Ottoman Empire, and successfully bypassed their reliance on land-trade by discovering maritime routes around Africa and towards the Americas.
The first naval action in defense of the new colonies was just ten years after Vasco da Gama's epochal landing in India. In March 1508, a combined Gujarati/Egyptian force surprised a Portuguese squadron at Chaul, and only two Portuguese ships escaped. The following February, the Portuguese viceroy destroyed the allied fleet at Diu, confirming Portuguese domination of the Indian Ocean.
In 1582, the Battle of Ponta Delgada in the Azores, in which a Spanish-Portuguese fleet defeated a combined French and Portuguese force, with some English direct support, thus ending the Portuguese succession crisis, was the first battle fought in mid-Atlantic.
In 1588, Spanish King Philip II sent his Armada to subdue the English fleet of Elizabeth, but Admiral Sir Charles Howard defeated the Armada, marking the rise to prominence of the English Royal Navy. However it was unable to follow up with a decisive blow against the Spanish navy, which remained the most important for another half century.  After the war's end in 1604 the English fleet went through a time of relative neglect and decline.

In the 16th century, the Barbary states of North Africa rose to power, becoming a dominant naval power in the Mediterranean Sea due to the Barbary pirates. The coastal villages and towns of Italy, Spain and Mediterranean islands were frequently attacked, and long stretches of the Italian and Spanish coasts were almost completely abandoned by their inhabitants; after 1600 Barbary pirates occasionally entered the Atlantic and struck as far north as Iceland.
According to Robert Davis as many as 1.25 million Europeans were captured by Barbary pirates and sold as slaves in North Africa and the Ottoman Empire between the 16th and 19th centuries. These slaves were captured mainly from seaside villages in Italy, Spain and Portugal, and from farther places like France, England, the Netherlands, Ireland and even Iceland and North America. The Barbary pirates were also able to successfully defeat and capture many European ships, largely due to advances in sailing technology by the Barbary states. The earliest naval trawler, xebec and windward ships were employed by the Barbary pirates from the 16th century.

From the middle of the 17th century competition between the expanding English and Dutch commercial fleets came to a head in the Anglo-Dutch Wars, the first wars to be conducted entirely at sea. Most memorable of these battles was the raid on the Medway, in which the Dutch admiral Michiel de Ruyter sailed up the river Thames, and destroyed most of the British fleet. This remains the greatest English naval defeat, and established Dutch supremacy at sea for over half a century. Very few ships were sunk in naval combat during the Anglo-Dutch wars, as it was difficult to hit ships below the water level; the water surface deflected cannonballs, and the few holes produced could be patched quickly. Naval cannonades damaged men and sails more than they sunk ships.

Late modern: 

18th century: The 18th century developed into a period of seemingly continuous international wars, each larger than the last. At sea, the British and French were bitter rivals; the French aided the fledgling United States in the American Revolutionary War, but their strategic purpose was to capture territory in India and the West Indies – which they did not achieve. In the Baltic Sea, the final attempt to revive the Swedish Empire led to Gustav III's Russian War, with its grande finale at the Second Battle of Svensksund. The battle, unrivaled in size until the 20th century, was a decisive Swedish tactical victory, but it resulted in little strategical result, due to poor army performance and previous lack of initiative from the Swedes, and the war ended with no territorial changes.
Even the change of government due to the French Revolution seemed to intensify rather than diminish the rivalry, and the Napoleonic Wars included a series of legendary naval battles, culminating in the Battle of Trafalgar in 1805, by which Admiral Horatio Nelson broke the power of the French and Spanish fleets, but lost his own life in so doing.

19th century: Trafalgar ushered in the Pax Britannica of the 19th century, marked by general peace in the world's oceans, under the ensigns of the Royal Navy. But the period was one of intensive experimentation with new technology; steam power for ships appeared in the 1810s, improved metallurgy and machining technique produced larger and deadlier guns, and the development of explosive shells, capable of demolishing a wooden ship at a single blow, in turn required the addition of iron armour.
Although naval power during the Song, Yuan, and Ming dynasties established China as a major world seapower in the East, the Qing dynasty lacked an official standing navy. They were more interested in pouring funds into military ventures closer to home (China proper), such as Mongolia, Tibet, and Central Asia (modern Xinjiang). However, there were some considerable naval conflicts involving the Qing navy before the First Opium War (such as the Battle of Penghu, and the capture of Formosa from Ming loyalists).
The Qing navy proved woefully undermatched during the First and Second Opium Wars, leaving China open to de facto foreign domination; portions of the Chinese coastline were placed under Western and Japanese spheres of influence. The Qing government responded to its defeat in the Opium Wars by attempting to modernize the Chinese navy; placing several contracts in European shipyards for modern warships. The result of these developments was the Beiyang Fleet, which was dealt a severe blow by the Imperial Japanese Navy in the First Sino-Japanese War (1894–1895).
The battle between CSS Virginia and USS Monitor in the American Civil War was a duel of ironclads that symbolized the changing times. The first fleet action between ironclad ships was fought in 1866 at the Battle of Lissa between the navies of Austria and Italy.