The image of lost treasure in shipwrecks under miles of ocean water can easily be imagined thanks to the visual effects of Hollywood movies. The magnificent structures of shipwrecks actually exist deep under the ocean, lost to the darkness and animals which inhabit the rotting vessel.
Shipwrecks may cause the ship to sink, leave it stranded on rock, land, or shoal or even cause it to be completely destroyed due to rough winds and waves from violent weather. The causes of shipwrecks are many which may range from human error to nature’s fury. Depending on various factors, the ships and its contents may be well preserved or completely deteriorated. An adventurous group of shipwreck hunters have not only made a profession but possibly an obsession of finding these ghosts of the sea and the treasures they hold within.

Types of Shipwrecks

Historical Shipwrecks: Shipwrecks which are more than 50 years old are classified as historical and are protected by UNESCO Convention of the Protection of Underwater Cultural Heritage from looting. These ships provide archeologists and historians a look into the past. The Mary Rose, which was recovered in 1982, provided great information about seafaring, warfare and life in the 1500’s.

Military Shipwrecks: Military shipwrecks provide insights into previous battles during war. They are generally off-limits except to scientific teams. Most countries classify them as spoils of war, the US however declares all its ships as its own property. An example of a military shipwreck is the USS Alabama which sank off the coast of France in 1864.

Treasure Shipwrecks: Ships under this category sank during the period of European Colonization. Under international maritime law, treasure shipwrecks belong to the finder of the wreck if they apply for a salvage claim. The initial owners lose all rights to the ship. One of the most well known shipwrecks was a fleet of 32 Spanish ships, one of them the famous El Dorado. Due to cyclone winds the entire fleet went down, with it a gold table reported to be 1.5 tons. Along with 3 million dollars worth of gold and pearls.

Contemporary Shipwrecks: Due to advancements in technology and research, shipwrecks in this day and age are becoming less common. Some ships are sunk deliberately to create a foundation for coral reefs. These wrecks are common amongst recreational divers for exploration purposes. The Adolphus Busch, sunk off of the coast of Florida, is such an example.  

Abandoned Shipwrecks: Abandoned shipwrecks are those which the owner has disowned. These are usually small fishing ships and are scattered in large numbers throughout the world.

Wreck Detectives: The Discovery Channel’s insight into shipwrecks with information on 5 famous shipwrecks.
Shipwreck Expo: A guide to shipwrecks located in the US. For those who can’t travel there this site provides a fun look into the wrecks with 3-D images.
Shipwrecks: A brief introduction to shipwrecks and the treasure found within.
Archeology World: Types of shipwrecks and other information.
Shipwrecks and Sea Rescue: An introduction to shipwrecks and sea rescues categorized by year. This site also provides interesting photos with the option to save them to your own profile.

Causes of Shipwrecks

Understanding the causes of shipwrecks has made travelling on the seas and oceans far safer now than in previous times. There are numerous causes for shipwrecks which can be prevented, though some will always pose a threat to those who decide to travel by ship.
Improving the design and the equipment of the ship continues to be one way to make travelling safer. Making sure that cargo is stored properly, the ship is not overloaded, and the cargo can’t shift suddenly can also be controlled. Factors which cannot be controlled include bad weather, warfare, fires and piracy.
Northern Maritime Research: A simplified look into the causes of shipwrecks
Sea Research Society: An online magazine for research, exploration and discovery
The Human Factor in Shipwrecks and Other Accidents to Ships: (.pdf file) A detailed paper on the human factors involved in a shipwreck
An Inquiry into the Causes of Shipwrecks: Its implications and prevention of pollution
Shipwrecks: (.pdf file) Lesson plan of causes of shipwrecks in the past

Factors Determining State of Preservation of Shipwreck
There are many different factors which affect how well a ship has been preserved. These include:
The construction material of the ship: Unless covered in sand or silt, the wooden structures of ships tend to decay very quickly in water. Portions of a ship which are made of steel usually last longer, even for many decades. However, even the steel portions of the ship may collapse where corrosion occurs.
The amount of destruction at the time of the wreck: When ships experience severe destruction at the time of the wreck, the preservation of the shipwreck is negatively affected. Severe damage can occur due to collision with another ship, major explosions, long burning fires, and impact against objects such as reefs, icebergs, and other large masses.
Water factors where the wreck occurred including salinity, depth, tide, and temperature: Ships which have been wrecked in sea water decay faster than those in freshwater. In fact, freshwater wrecks remain nearly perfectly intact. Wrecks deep in the sea degrade faster due to higher oxygen levels and strong currents, both of which speed up corrosion. Wrecks in very cold water, such as those near glaciers, degrade significantly slower than those in warmer waters.

Great Lakes Shipwreck Preservation Society: Dedicated to preserving shipwrecks
Shipwreck Diving: All about artifact preservation, including bronze, brass, ceramics, glass, gold, silver, leather and more.
Wreck Diving Holidays: The ultimate collection of holidays to view preserved shipwrecks

Famous Shipwrecks throughout History

The Mary Rose: The Mary Rose is one of the most famous shipwrecks in history. It was a favorite warship of King Henry VIII and said to be “the fairest flower of all the ships that ever sailed”. In July 1545 King Henry watched his favorite ship sink due to a squall of wind. There were 700 people on board, from which approximately 40 survived. Salvage operations started in the same year and later halted. The efforts started again in the 1960’s and by 1982 the ship was recovered. It is now on display at the Portsmouth Dock.

The Titanic: Everyone has probably heard of the Titanic. Its famous story has been the setting of many books and movies. The ship was constructed to ferry passengers between Southampton and New York. On her maiden voyage in April 1912 the Titanic struck an iceberg and sank. There were 2,200 passengers and crew onboard from which only 700 survived. In 1985 the wreck was located by a joint French-American expedition. Approximately 6,000 artifacts have been removed from the wreckage, most of which are on display at the Greenwich Museum in England.

The Lusitania:  The Lusitania was a British ship sailing from New York to Liverpool and was sunk by a German torpedo in May 1915. The massive ship sank within 20 minutes and the lives of 1,201 passengers including women and children were lost. Though the ship was carrying ammunition, it was operating as a civilian liner. It was one of the reasons which caused the US to hurry its involvement in World War I, since 128 of the passengers were American. The wreck has never been salvaged though numerous photos have been taken.

The Bismarck: The Bismarck warship was the pride of the German navy. She was the length of three football fields and stood 17 storey’s high. On her maiden voyage of 8 days in May 1941 the warship was crippled by a British attack and sank against an undersea mountain. Of the 2,200 men on board only 115 survived. The wreck was discovered in 1989 by Dr. Robert Ballard who also discovered the Titanic.

Wreckhunters: Hunting New England’s shipwrecks - A guide for divers and armchair adventurers.
Ocean Treasures: Shipwrecks and lost treasures of the seven seas
Bridging Our Historical Past Through Shipwrecks: A well organized database with information on data collection techniques and background information.
Famous Shipwrecks: A database on famous shipwrecks
Historical Shipwrecks: Oracle Thinkquest, a project for students by students provides a database of shipwrecks along with links to other sites.

Further Resources
The Ships List: A database of shipwrecks and passenger records with a separate listing of the crew members and even a navy crew list.
DeepImage Shipwreck Exploration: Underwater shipwreck exploration, filming and photography
Exploring Shipwrecks: (.pdf file) A teachers guide to explaining shipwrecks
Metal Detecting World: All about shipwreck diving and treasure hunting including information on types of shipwrecks, underwater communication and diving navigation.
Savage Seas: Surviving in stormy seas from the angle of ship design and the human factor.
Ships of Discovery: Christopher Columbus’s lost ships
Archeology: Information on Bronze Age shipwrecks