Breath-hold diving is a sport activity avallable to every swimmer, not requiring any special technical equipment. In its competitive form, brath-hold diving (also apnea diving or freediving) has a number of disciplines in which divers compete both in the pool and in the outdoor natural waters.
The most serious risk is a sudden and unobserved loss of consciousness, the so-called diving blackout. It can have lethal consequences if the diver does not immediate help.
The basic preventive measures of these events are never to dive without the supervision of another person, never to hyperventilate before immersion below the water surface and possibly complete a diving course under the supervision of a certified professional instructor.