repairs are usually minor. They are done on the submerged parts of a ship
(the propeller), the rudder of the ship, the cathodic protection system,
etc.), on oil platforms and other pieces of machinery. Only special teams
or groups of experienced divers can do such tasks because there is certain
knowledge that must be acquired for the accomplishment of the repair. Usually,
the task starts with an inspection of the working spot, selection of methods
and instruments, planning the operation, the doing of the task and checking
whether everything is on order.
Such repairs are often done
in ports (not in open sea). There are some demandings for the safety of
divers: the propeller should be locked, the ship should be stable and no
objects should be thrown over board when there is a diver under water.
Sometimes, it is also recommended to have a means of attachment to the
side of the ship - a line or magnets.
Below you see pictures of
divers repairing the hull of a ship. The Earth emits magnetic field which
damages the hull of the moving ship. That is why, divers apply protectors
made of brass to it. When the alloy is worn over, divers coat the hull
with new protectors.
The salvage of a sunken
ship, plane, submarine, cargo, etc. from the sea bottom is performed in
several ways. The choice of technique is conformable to the weight and
volume of the item. There are four main ways of salvaging - using the line
to tie the object and lift it, attaching a flotation device to it, restoring
the flotation of the sunken object. If it is small and light, the diver
can carry it to the surface. Sometimes, if the object is buried in silt,
the silt is cleared with the help of a water jet or an air hose. When salvaging
an item, the diver should be very careful not to swim under it because
in case of accident, the object might start to sink and hurt the diver.
Other industrial procedures
include building bridges, ports, oil platforms, underwater mining, repairing
flooded underground facilities (subway).