Marine salvage
[4] The common law concept of salvage was established by the English Admiralty Court and is defined as "a voluntary successful service provided in order to save maritime property in danger at sea, entitling the salvor to a reward"; this definition has been further refined by the 1989 Convention.
Since 2000, it has become standard to append a SCOPIC ("Special Compensation – P&I Clubs") clause to the LOF to ensure that a salvor does not abuse the aforementioned environmental policy stated in the 1989 Convention (pursuant to the case of The Nagasaki Spirit).
[5] The techniques applied in marine salvage are largely a matter of adapting available materials and equipment to the situation, which are often constrained by urgencies, weather and sea conditions, site locations, and financial considerations.
[16] Despite this, many shipwrecks from World War II near Indonesia — where most of the water is shallower than 80 metres (260 ft)— are threatened by scavenging for low-background steel for use in medical and scientific equipment.
[17] During World War I, a Royal Navy team of covert divers led by GCC Damant salvaged intelligence materials[clarification needed] from recently sunken U-boats.
The CIA, who conducted the salvage under the guise of mining the seafloor for manganese nodules with a commercial vessel, spent over $800 million in 1974 on the clandestine operation now known as Project Azorian.
It is in some ways similar to the wartime law of prize — the capture, condemnation and sale of a vessel and its cargo as a spoil of war, insofar as both compensate the salvor/captors for risking life and property.
[22] Marine salvage requires the salvor to acclimatize to the situation, and the job is often constrained by urgency, weather and sea conditions, site accessibility, and financial considerations.
[6]: Ch.10 When all or part of the main deck of a sunken ship is submerged, flooded spaces cannot be cleared until all openings are sealed or the effective freeboard is extended above the high water level.
14 The usual methods for wrecking in place are manual flame cutting by divers and surface workers, demolishing using heavy lift cranes, explosive sectioning, dispersal, or flattening, and hydraulic dredging near the burial or settling.[6]: Ch.
Side-scan sonar uses acoustic transducers towed underwater to produce a plan view image of the seafloor showing details of the topography and artifacts at the sides of the track.
A laser-imaging system utilizes a blue and green laser as the illumination source to minimize attenuation and backscattering problems and can image targets as far as 50 meters away in good conditions.
[27] Trailing the hydrophones behind the vessel on a cable that can be kilometers long keeps the array's sensors away from the ship's own noise sources, greatly improving its signal-to-noise ratio, and hence the effectiveness of detecting and tracking faint contacts, such as quiet, low noise-emitting submarine threats, or seismic signals.
The "Z" search makes use of the linear nature of pipelines and cables by ensuring that the towed sensor will cross the object several times at a reasonable angle for detection.
It provides a margin of safety to mitigate ship track and sensor tow path variations and compensates for the inherent loss in the sonar signal quality at the outer ranges.
The underwater endurance of freedivers was mainly extended by the use of diving bells and engines, which either carried a small volume of air inside, or were laboriously replenished from weighted barrels, severely limiting maximum operating depth and duration.
A rare exception to this was William Phip's successful recovery of twenty-six tons of silver in 1687, which inspired a large number of unsuccessful treasure hunts, most of which lost the investors' money.
Since the pre-industrial technology severely limited underwater time and mobility and lifting capacity, salvors concentrated on high-value, low bulk cargoes, particularly non-ferrous metals, which retain their value even after long immersion.
The available technology made it difficult to recover cargo in environments like rocky lee shores and shallow reefs, which were common sites for ships to be driven ashore.
A cast copper diving bell used by Francisco Nunez Melián in 1624 for salvage of the cargo of the Santa Margarita in the Florida Keys is recorded to have weighed 680 lb (310 kg) and cost 5000 reales.
[33] In 1687, Sir William Phipps used an inverted container as a diving bell to recover £200,000 worth of treasure from a Spanish ship sunk off the coast of San Domingo.
[33] The era of modern salvage operations was inaugurated with the development of the first surface supplied diving helmets by inventors Charles and John Deane as well as Augustus Siebe, in the 1830s.
At the British Association for the Advancement of Science meeting in 1842, Sir John Richardson described the diving apparatus and treatment of diver Roderick Cameron following an injury that occurred on 14 October 1841 during the salvage operations.
A specially-built armoured suit, or observation bell, called torretta butoscopica, was used with a diver inside who was able to direct the salvage operations and the placing of explosives to blast the ship open to expose the strong room.
: 152 In April 1941, in the face of British Army advances in the East African campaign, Italian Rear Admiral Mario Bonetti successfully blocked the Red Sea harbour of Massawa by scuttling 18 large commercial ships, 13 smaller coastal vessels, a floating crane, and two critically important dry docks.
However, the British civilian salvage team spent a fruitless year struggling against the oppressive heat and humidity, which persistently caused multiple industrial air compressors to fail, dropping half-floated ships back to the harbour silt.
[44] In 1943–1944, the Great Lakes salvage engineer, Captain John Roen, did what was considered financially impossible and salvaged SS George M. Humphrey, which sank in a collision in 23 metres (77 ft) of water in the Straits of Mackinac, by first removing the ore it was carrying and then using two vessels on each side of the underwater wreck, with cables that "walked" George M. Humphrey in stages underwater to shallower water where it was then pumped out and re-floated and towed out.
The remains of the ship, together with recovered weapons, sailing equipment and crew's personal effects are now on display at Portsmouth Historic Dockyard and the nearby Mary Rose Museum.
The artifacts ranged from tiny brass sewing pins and glass buttons to heavy iron cannons and included such things as cannonballs, bullets, bottles, pottery, carved bone toothbrushes, pencils, match cases, and Wedgwood china.
It was towed, stern first to Newcastle, New South Wales, in August 2002 for minor repairs,[60] and was consequently returned to the United Kingdom aboard the heavy lifting vessel MV Swan.
