موضوع
تعبير عن cave
diving
موضوع تعبير عن cave diving
Underwater
diving
Underwater
diving is an extreme sport in which a diver visits networks of cavities and
caves filled with water. The equipment used varies with the circumstances, and
varies depending on the range required for the return to the surface, but
almost all the underwater dives are carried out using diving equipment, with
specific configurations. Underwater diving is generally considered a type of
technical dive because it takes place under the ceiling in non-free water,
during most of the dive, and often involves decompression.
In France we
have a lot of dive site, in the Lot for example, this is also called diving
caving. England is also well known for this type of activity, like the United
States and Mexico with their huge networks in Florida. Compared to dry caving
and scuba diving, there are relatively few underwater diving practitioners.
This is due in part to specialized equipment (such as rebreathers, scuba diving
scooters and dry suits) and skill sets needed, and partly because of high
potential risks, including decompression and drowning.
Despite
these risks, water-filled caves attract divers, cave enthusiasts and cavers
because of their often unexplored nature, and present divers with technical
diving challenges. Underwater caves have a wide range of physical features, and
may contain wildlife not found elsewhere.
The dangers
of cave diving
Kilometers
long and ramifications for underground networks
Kilometers
long and ramifications for underground networks
Underwater
diving is one of the most difficult and potentially dangerous types of diving
or caving and presents many dangers. Underwater diving is a form of penetration
diving, which means that in case of emergency a diver can not swim vertically
to the surface due to the ceilings of the cave, and therefore must swim all the
way back. Underwater navigation through the cave system can be difficult and
exit routes can be at a considerable distance, forcing the diver to have enough
breathing gas to make the return trip. The dive can also be deep, which leads
to potential risks of deep diving.
Visibility
can vary from almost unlimited to low or nonexistent, and can go from one
extreme to the other in a single dive. Even though a less intensive type of
diving called cave diving does not lead divers out of the reach of natural
light (and usually no deeper than 40 meters, and for a maximum penetration of
60 meters), true cave diving may involve penetrations of several kilometers,
far beyond the reach of daylight. The level of darkness created creates an
environment impossible to see without multiple sources of lighting. Caves often
contain sand, mud, clay, silt or other sediments that can further reduce
underwater visibility in a few seconds when shaken.
Underground
rivers can be crossed by very strong currents of water. Most caves emerge on
the surface as springs or siphons. The springs have flowing currents, where the
water comes out of the Earth and flows through the surface of the earth to
throw itself into the rivers. Siphons have incoming currents where, for
example, a surface river passes underground. Some caves are complex and have
tunnels with outgoing currents, and other tunnels with incoming currents. If
the currents are not properly managed, they can cause serious problems for the
diver.
Underwater
diving has been perceived as one of the deadliest sports in the world. This
perception is questionable because the vast majority of divers who lost their
lives in the caves did not receive specialized training or had inadequate
equipment for the environment. Underground divers have suggested that cave
diving is in fact statistically much safer than recreational diving because of
the much greater barriers imposed by experience, training and cost of equipment.
There is no
reliable global database that lists all cave diving deaths. However, such
fractional statistics suggest that very few divers died using accepted
protocols and using equipment configurations that are acceptable to the
underground divers community.