A shipwreck can either refer to the event of a ship being wrecked, or the physical wreck itself. Shipwrecks have occurred throughout maritime history, and it is likely that millions have died by them. The United Nations estimates that there are 3 million shipwrecks on the ocean floor all over the world. Some of these have become prime diving spots, as many sea organisms will encrust a shipwreck if provided with one. Some known shipwrecks are very old, including Greek merchant ships dating to 400 BC, Phoenician shipwrecks dating to 1200 BC, and a Levantine shipwreck dated to 1400 BC, the late Bronze Age.
There have been many famous shipwrecks throughout history, and there are many atolls throughout the world with dozens, if not hundreds, of wrecks in their shallows. Wrecks happen for any number of reasons, usually in storms, running aground from poor navigation, or due to enemy attacks during war. Probably the most famous wreck in history is the HMS Titanic, an 882 ft (269 m) luxury cruise ship that sunk in the North Atlantic after striking an iceberg. The shipwreck killed 1,500 people, and the ship sank about 2.5 miles (4 km) to the ocean floor. Many years later, in 1982, the Titanic was photographed and investigated in place by a remotely operated deep sea submersible. Periodically, the idea of lifting the wreck back up to the surface has been discussed, but putting in the effort would probably require hundreds of millions of dollars.
The study of old shipwrecks and other sunken artifacts is a whole discipline known as maritime archeology. Studying ancient shipwrecks can give us a lot of information about a lost civilization, preserving cultural objects that would have long ago been looted and consumed or disassembled if left on land. One of the most famous objects from an ancient shipwreck, the Antikythera mechanism, is actually the first known mechanical computer, and was used to compute the cycles of the Sun, Moon, and planets. The precision and complexity of the gears is considered on par with 17th century watches, and mechanisms of similar complexity do not appear in the archaeological record until over 1000 years later.
Some artifacts that have been discovered from shipwrecks dating back to antiquity include large quantities of gold, Egyptian ebony for furniture, ostrich eggs, amber, unworked glass, various resins for perfume or incense, ivory vessels, clay lamps, jewelry, bronze carpentry tools, spears, swords, ceremonial axes, and hundreds of other objects. Many of these fascinating finds can now be found in museums throughout the world.