Wreck diving
Professional divers, when diving on a shipwreck, generally refer to the specific task, such as salvage work, accident investigation or archaeological survey.
However, there is clearly a much greater risk of entanglement and silt out inside of the structure, as well as the requirement to move laterally to a defined exit point before one can surface in the event of an emergency.
[2] These categorisations broadly coincide with the traditional division between "recreational" wreck diving (taught as a specialty course by recreational diver training agencies and normally limited to the "light zone" and/or 100-130 cumulative feet of depth plus penetration) and "technical" wreck diving (taught as a stand-alone course by technical diver training agencies).
For penetration diving, a reserve of breathing gas sufficient to allow the diver to exit the wreck and make a safe ascent in the event of any reasonably foreseeable single failure of equipment is required by training agencies' protocols and scientific codes of practice.
[11] An alternative approach, popularised to a limited extent by deep wreck divers in the American Northeast, is referred to as "progressive penetration".
The method is vulnerable to complete loss of visibility in a silt-out, and any disorientation in an unfamiliar area or due to nitrogen narcosis.
This creates the possibility of a diver being unable to relocate their decompression gases if they exit the wreck at a different point from which they enter it.
Other technical diving organizations, such as IANTD, TDI and ANDI teach advanced wreck courses that require more extensive training and competence and more safety equipment, and prepare divers for levels of wreck penetration beyond the areas illuminated by ambient light.
In this context, some research projects are investigating the potentialities offered by digital technologies to adopt virtual replicas of the underwater wrecksite for training purposes.
For example, if the wreck is at a depth that is classified as technical deep diving, then the basic equipment requirement will be based on that.
Additional breathing gas for the rule of thirds in an overhead environment increases the required cylinder size.
This may be in the form of buddy or team supplied reserve gas or as a bailout cylinder carried by the diver For full penetration diving, additional safety equipment is necessary.
Equipment should be stowed compactly, to reduce the risk of snagging on wreckage and being damaged or trapping the diver.
[citation needed] In South African waters, the wrecks of ships or aircraft, and any associated cargo, debris or artifact more than 60 years old and are protected by the National Heritage Resources Act number 25 of 1999 (NHRA).
[19] The law of salvage and finds does not apply to historical shipwrecks, which are considered by the NHRA to be archaeological material, and as such are the property of the state, administered by SAHRA in trust for the nation, and may not be disturbed in any way except under the terms of a permit issued by the South African Heritage Resources Agency (SAHRA).
Historical wrecks may be visited provided that the sites are not disturbed or interfered with and no artifacts are removed or damaged.
"[23] Along the Outer Banks, navigational challenges posed by the Diamond Shoals area off Cape Hatteras, caused the loss of thousands of ships and an unknown number of human lives.
[24] Among the better known shipwrecks was USS Monitor,[25] a participant in the Battle of Hampton Roads during the American Civil War.
During World War II German U-boats would lie offshore and silhouette passing freighters and tankers against the lights onshore.
[26] Others are wrecks of vessels lost in disasters (such as RMS Rhone in the British Virgin Islands, Zenobia in Cyprus and the many shipwrecks off the Isles of Scilly in England).
In the Marlborough Sounds, New Zealand, the wreck of MS Mikhail Lermontov, a 177-metre (581 ft) cruise liner which was lost in 1986, is a popular dive site.
Lying at 37 metres (121 ft) underwater, this wreck is an excellent base for recreational and technical divers.
[citation needed] A number of wreck diving sites are ships lost to wartime hostilities, such as SS Thistlegorm in the Red Sea, the wrecks of Subic Bay and Coron in the Philippines, SS President Coolidge in Vanuatu and the "ghost fleet" of Truk Lagoon.
[citation needed] Some regions are particularly noted for the number and quality of wreck dive sites, such as Truk Lagoon in Micronesia, Scapa Flow in Orkney Islands, Scotland, the Outer Banks of North Carolina, known as the "Graveyard of the Atlantic", and the Great Lakes.
