What is scuba diving

Scuba diving is the term used to describe the use ofabout 500 B.C.) is perhaps the most famous, as told
a self-contained breathing set to stay underwater forby the 5th century B.C. Greek historian Herodotus
periods of time greater than the average individual(and quoted in numerous modern texts).
can breath-hold. The diver carries all equipmentDuring a naval campaign the Greek Scyllis was taken
necessary for diving and is not reliant upon equipmentaboard ship as prisoner by the Persian King Xerxes I.
elsewhere (e.g. on the surface) to supply breathingWhen Scyllis learned that Xerxes was to attack a
gas or other support during the dive. The diverGreek flotilla, he seized a knife and jumped
swims underwater using fins attached to his/her feet.overboard. The Persians could not find him in the
Some divers also move around with the assistancewater and presumed he had drowned. Scyllis
of a DPV (Diver Propulsion Vehicle), commonlysurfaced at night and made his way among all the
referred to as a "scooter", or by usingships in Xerxes' fleet, cutting each ship loose from its
surface-tethered devices called sleds, which are pulledmoorings; he used a hollow reed as snorkel to remain
by a boat.unobserved. Then he swam nine miles (15 kilometers)
The word 'SCUBA' is an acronym for "Self Containedto rejoin the Greeks off Cape Artemisium.
Underwater Breathing Apparatus", but it has becomeThe desire to go under water has probably always
acceptable to refer to 'scuba equipment' or 'scubaexisted: to hunt for food, uncover artifacts, repair
apparatus'. The term SCUBA in common usage usuallyships (or sink them), and observe marine life. Until
means open-circuit equipment in which gas (usuallyhumans found a way to breathe underwater,
air) is breathed from a tank of compressed gas andhowever, each dive was necessarily short and frantic.
then exhaled into the water, usually in the line of kitOne of the major hurdles of diving is to stay under
development started by Emile Gagnan andwater for a longer period of time. Breathing through
Jacques-Yves Cousteau. But rebreathers (botha hollow reed allows the body to be submerged, but
semi-closed circuit and closed circuit) are alsoreeds more than two feet long do not work well;
self-contained systems and could be classed asdifficulty inhaling against water pressure effectively
SCUBA. The term SCUBA arose during WWII andlimits snorkel length. Breathing from an air-filled bag
originally meant USA combat frogmen's oxygenbrought under water was also tried, but it failed due
rebreathers.to rebreathing of carbon dioxide and the buoyancy
Or surface-supplied systems may be used dependingof the air bag.
on the needs of the diver.In the 16th century people began to use diving bells
Scuba diving is still evolving, but general classificationssupplied with air from the surface, the first effective
have grown up to describe the pursuits a diver mightmeans of staying under water for any length of time.
follow. These classifications include, but are not limitedThe bell was held stationary a few feet from the
to:surface, its bottom open to water and its top portion
Within recreational diving there are those who arecontaining air compressed by the water pressure. A
considered professional divers, because they maintaindiver standing upright would have his head in the air.
a professional standard of training and skills (andHe could leave the bell for a minute or two to collect
must, in theory, according to the laws of the area,sponges or explore the bottom, then return for a
carry professional liability insurance).short while until air in the bell was no longer
Some consider Technical Diving to be a subset ofbreathable.
recreational diving, but others separate it out due toIn 16th century England and France, full diving suits
the extensively different training equipment andmade of leather were used to depths of 60 feet. Air
knowledge needed for technical dives.was pumped down from the surface with the aid of
Public safety diving and military diving might likewisemanual pumps. Soon helmets were made of metal to
be classified as commercial diving because publicwithstand even greater water pressure and divers
safety divers and military divers make a living fromwent deeper. By the 1830s the surface-supplied air
their pursuit of diving. However, public safety divershelmet was perfected well enough to allow extensive
(police or rescue) and military divers have a differentsalvage work.
mission from the typical commercial diver.Starting in the 19th century, two main avenues of
Scientific diving is used by marine scientists, includinginvestigation - one scientific, the other technological -
marine biologists, as a tool for collecting their researchgreatly accelerated underwater exploration. Scientific
data.research was advanced by the work of Paul Bert
History of divingand John Scott Haldane, from France and Scotland,
Men and women have practiced breath-hold divingrespectively. Their studies helped explain effects of
(Free-diving) for centuries. Indirect evidence comeswater pressure on the body, and also defined safe
from ancient artifacts of undersea origin found onlimits for compressed air diving. At the same time,
land (e.g. mother-of-pearl ornaments), and depictionsimprovements in technology - compressed air pumps,
of divers in ancient drawings. In ancient Greece,carbon dioxide scrubbers, regulators, etc., - made it
breath-hold divers are known to have hunted forpossible for people to stay underwater for long
sponges and engaged in military exploits. Of theperiods.
latter, the story of Scyllis (sometimes spelled Scyllias;