Here's a paper I wrote sometime back on one of my favorite subjects:
An Overview of Maritime Archaeology
History is the key to the future, as the phrase goes, and this is the foundation for every archaeologists' motivation. Their quest is to find answers to their questions, and in maritime archaeology, the answers often lay at the bottom of the sea, ocean, lake, or even pond, and, not surprisingly, their commitment to the search leads them all over the world.
Maritime Archaeology is like a mystery novel, consisting of "crime scene" (which is the wreck), "evidence" (the artifacts), and "research" (history, in this case); an archaeologist is the detective, responsible for paring them all together and solving the case to find out: Who owned it, captained it, and was aboard it; What: the specifics of the ship, its name, width, length, etc; When: all the dates involved, when it was built, launched, and wrecked; Why: the reasons for its demise; and How: the details of its demise. There is much more one could ask, but regarding the basics, an understanding of the science is necessary.
Maritime Archaeology Defined-- Archaeology is the study of ancient life through the means of excavation; maritime archaeology is a sub category, it is everything archaeology is except in or near water. Further categories include underwater archaeology and nautical archaeology, of which the first addresses the past through submerged remains and the second through vessel construction and use.
The most common objectives in maritime archaeology are shipwrecks. Since air travel wasn't a possibility until the 1900's, the seas and lakes of our world were highly trafficked as a means of survival and livelihood. As can only be expected, ships went down because of tempests and rocky coasts, plus failure to properly handle the ship, and sadly, so much more. One ship in particular was destroyed as a result of carelessness. A sailor dropped a lantern in the spirit locker, and the fire reached the powder magazine and burnt the ship, HMS Serapis, to her waterline before she drifted to the depths of the Indian Ocean. In warm, shallow waters, wood is easily destroyed by marine worms and other sorts of aquatic life, but in most deeper waters, when this happens, because of the cool water temperature and the lack of marine life, the ship is preserved, suspended in time waiting to be discovered years later. Thus the reason they have been termed "time capsules".
On The Job-- However, before an archaeologist can give thought to excavation, one must first consider what will be needed, and depending upon the nature of the site, the equipment required will vary. Diving equipment and skill is a must and if the site is not able to be reached by land (e.g. a shore-side wreck), a boat should be next on the list but the size of the boat is a question of affordability. In large scale situations where the site is massive, or in deep water, or both, more advanced technology is required, such as a large support vessel with equipment handling cranes, underwater communications, computer visualization, ROV's (Remotely Operated Vehicles), and sometimes on rarer occasions the use of a submarine is required. But maritime archaeology doesn't always demand such radical paraphernalia, it can function on a much smaller scale.
First off, fixing the position of the site is necessary for present efficiency and future reference. This can be accomplished with a standard GPS devise. After that is a survey of the site and sometimes this includes testing the waters for harmful chemicals, but this is usually only the case with more recent wrecks where the ships were made of metals. The simple form of survey is using depth gauges and tape measures, and though not 100% accurate, it does the job satisfactory. Once the area is graphed, the next step is recording the site. One way is scale drawing with pencil and special underwater paper, but an easier and more advanced method is photography. Making a mosaic or photo-montage of the site can help a lot in the hours of lab work to come. And recording must continue through the rest of the steps of archaeology as well. Knowing where an object was found will tell a great deal about that object and present vital information. If failure to properly record artifact locations occur, the archaeologist will encounter only confusion in later work. Only when basic recording of the site is finished can excavation begin. Once again, depending upon the nature of the site will a person know what is required but the water dredge is an effective choice. It removes the sand or dirt around specific artifacts whereas on land one might use a shovel. It also collects tiny objects that might otherwise be missed sending them to the boat above for careful sorting. The handler of the dredge in the boat must beware, though, many a time have they met with an unexpected visitor of the world below. Squids, for example have been known to make it up the hose.
The hardest part is yet to come. It involves research and sorting and categorizing all that has been gathered. This in itself can take more time than the field work. Conserving the artifacts is a method all its own and takes time, even more so for encrustations. Encrustations could be described as growth from the ocean melding one or more artifacts together. The larger the encrustation the longer it will take. It must be treated and carefully worked on, using pneumatic tools and even x-ray.
Preservation-- Notwithstanding the above, not always is a wreck retrieved from its place of long time berth; instead some are marked as preserves. They are considered underwater museums, welcome to divers of varying stages for sport or further research.
One reason to choose to preserve a wreck over salvaging it is when it has become part of the environment. On the other hand, there are times when salvaging the wreck is necessary. This is the case with wrecks in water too deep to safely dive in, or when the remains of the wreck are sparse and would be better suited to research if brought up. Also one might decide to salvage a wreck in shallow water. Here are two reasons this would be the case: one is nature and the other is man. The dangers posed by the former could be rounded off to wind, waves, and, in some places, ice. The reason for the latter is often because of fishermen. For fish populate wrecks and when the fishermen drop anchor over the wreck it often does extreme damage. Added to this is the danger of looters, people who have no consideration for the historical value of a wreck and its contents and only see the profit.
Other Maritime Archaeological Interests-- Aside from shipwrecks, the science of maritime archaeology delves into other cases such as sunken cities. Port Royal, for instance, which was the center of shipping commerce in the Caribbean during the later half of the 17th century, was hit by an earthquake in 1692. It sunk the northern section of the town and is now a means of great archaeological interest. Artifacts from as early as 1588 have been found there and to this day archaeologists are still continuing to excavate the city, with many "digs" still in progress.
In every case of archaeology, caution must be taken to secure the protection and proper care of the site and artifacts. A recommendation for maritime archaeologists would be to have a knowledge of history. Many answers will be provided to students of history, because as they say, history is the key to the future.