The collision of seagoing vessels and ships running aground or capsizing may result in a grave loss of life, property, and in some cases in ecological disasters. Some of these disasters may be the result of unfavourable weather conditions; a defect which affects the safety of the ship; failure to follow steering and sailing rules of navigation and right-of-way; or negligence with regard to the observance of good seamanship, including the duty to carry lights or signals and safety equipment, to keep a proper look-out, or to take any other precautions required by the ordinary practice of seamen or the special circumstances of the voyage. Some collisions may have their origin in other accidents, particularly if a damaged ship does not sink but becomes a drifting object constituting a menace to other vessels that might strike it.
In the decade ending 1989, 3,302 ships were lost worldwide (on average, one every day). In addition, many more vessels were victims of other marine casualties in which thousands of people were killed and many more injured. In 1988, of the fewest incidents since the 1960s, 230 ships sank and 760 people died in 52 of them.
Every year the equivalent of about a million tons of ocean-going vessels are lost at sea; this represents a greater fleet of ships than the individual fleets of nearly one hundred nations of the world. Although more precise navigational equipment and techniques are available today, larger vessels, increasingly crowded waters, and dangerous cargoes, aggravate the risk factors in shipping.