Ancient oared warship
A bireme is an ancient oared warship (galley) with two decks of oars, probably invented by the Phoenicians.Long vessels built for military purposes had relatively high speed, meticulous construction, strength, and depending on the number of rows of oars, were called uniremes, biremes, triremes, quadriremes, etc.
Experience soon proved that longer ships posed a new set of problems: They were weaker structurally, more difficult to maneuver, and presented a larger target to any enemy ship with a ram. In the 8th century BC Mediterranean shipbuilders eliminated these problems with the bireme, a war galley built to accommodate two levels, or banks, of oarsmen. Oarsmen on the lower level rowed oars from ports cut into the side of the vessel, while those above rowed from the deck. This arrangement allowed more men to power the bireme without lengthening the ship.
Underwater archaeology is a growing field. Underwater surveys and excavations of sunken ships and their cargo provide a wealth of information about ancient systems of trade. Sunken artifacts are often well preserved, protected by layers of silt in a stable environment of salt or fresh water.