First having read the book of myths, and loaded the camera, and checked the edge of the knife-blade, I put on the body-armor of black rubber   the absurd flippers   the grave and awkward mask.  I am having to do this like Cousteau with his assiduous team abourd the sun-flooded schooner   but here I am alone.  There is a ladder. The ladder is always there hanging innocently close to the side of the schooner. We know what it is for, we have used it. Otherwise it's a piece of maritime floss, some sundry equipment.   I go down. rung after rung and still the oxygen immerses me, the blue light, the clear atoms of our human air. I go down. my flippers cripple me, I crawl like an insect down the ladder and there is no one to tell me when the ocean will begin. First the air is blue and then it is bluer and then green and then black I am blacking out and yet my mask is powerful, it pumps my blood with power, the sea is another story, the sea is not a question of power,  I have to learn alone to turn my body without force in the deep element.  And now: it is easy to forget what I came for among so many who have always lived here, swaying their crenellated fans between the reefs and besides you breath differently down here.  I came to explore the wreck. The words are purposes. the words are maps. I came to see the damage that was done and the treasures that prevail. I stroke  the beam of my lamp slowly along the flank of something more permanent than the fish or weed, the thing I came for; the wreck and not the story of the wreck, the thing itself and not the myth, the drowned face always staring towards the sun     the evidence of damage worn by salt into this threadbare beauty     the ribs of disaster curving assertion among tentative haunters. This is the place. And I am here, the mermaid whose dark hair streams black, the merman in his armored body, We circle silently about the wreck, we dive into the hold. I am she; I am he whose drowned face sleeps with open eyes, whose breasts still bear the stress, whose silver, copper, vermeil cargo lies obscurely inside barrels, half winged and left to rot, we are half- destroyed instruments that once held course-- Shipwreck, by Adrienne Rich Locating The Shipwreck

 Nautical archaeologist use both old fashioned and modern methods  to locate wrecks.  Many times  information provided by  local sponge divers is more accurate then towed magnetometers and high-tech satellite imaging. 

Nautical Archaeologist realize that the most effective way to recognize and "see" objects  underwater is with sound. Underwater, light is rapidly diffused and very unproductive. Even the brightest lights give only a couple feet of visibility.  

Side scan sonar (Sound Navigation and Ranging) is a precisely engineered sonar designed to look through the water sideways, from both sides of a towed unit, to scan the bottom and the water above the bottom and produce an image of items of interest. This specialized sonar system for searching and identifying things on the sea-bed.   Side Scan Sonar throws out sound energy and studies the return signal that  springs back off the seafloor or other large submerged items.  The force of the return echo is constantly recorded generating a "portrait" of the sea floor where artifacts that stick out from the bottom create a dark image and shadows from these objects are light areas . While the shape of the seafloor and objects on it can be effectively represented, most side scan systems can not supply any real depth information. When a probable shipwreck is sited, a Remote Operated Vehicle  is sometimes used to complete a pre-disturbance study of the shipwreck location.

Mapping and Surveying the Underwater shipwreck

                                         Computer generated sea floor map

When nautical archaeologists locate a wreck site they need to establish  how big it is, and what it contains.  They survey the site and draw a map. They often use a method called triangulation. Triangulation involves drawing grids and taking many measurements from different fixed points around the site. The artifacts they find can later be drawn onto  the overall plan of the excavation. Some archaeologist use an approach called photo-mosaic. This method involves taking a series of overlapping photos of the wreck site, putting them altogether and building one big photograph of the site.

                                          

Nautical Archaeologist use many tools when they begin to excavate an underwater site. These tools include everything from good old buckets and shovels to high-tech  airlifts, water dredges  and water jets. The water dredge sucks up debris for later examination and works kind of like an ordinary vacuumed cleaner. The water dredge is used in both deep and shallow water excavations. 

The airlift is another important tool used during the excavation process.  A open tube descends  down to the excavation site. Compressed air is pumped from the surface into the lower end of tube thereby creating a suction.  Sand, water,  and little objects are later sifted and examined on deck.

According to  Jon Adams, Director, Centre for Maritime Archaeology Graduate program coordinator at the University of Southampton "The reason we abandoned the '-it-and-see' technique is because underwater sites often have so much organic material such as wood, leather, textiles, etc. If these go up an airlift they are likely to be damaged or
utterly destroyed. Certainly, we often fit sieves to airlifts and dredges but this is only to catch the small items we inadvertently miss (rather like land excavators sieving their spoil). The other reason we avoid putting objects up the tube is that it is often impossible to know where it came from and as you know, recording is one of the most important obligations an archaeologist has." 

Despite all these high-tech gadgets  many diver's consider their on their own hands to be their most valuable tool when it comes to locating underwater artifacts.