|
Scuba Diving
Helmet diving has the disadvantage of restricting the diver's lateral movement because of the connection to the surface. This fact led to the development of scuba (an acronym for self-contained underwater breathing apparatus). Scuba delivers air to the diver (from tanks of compressed air) at the same pressure as that exerted by the surrounding water. In this way the diver is able to descend to great depths without feeling the ill effects of high pressure (see skin diving). A skilled scuba diver with good equipment can descend as deeply as a helmet suit diver.
Record-setting dives of over 300 ft (91 m) have been made with scuba gear, although careful scuba divers do not go below about 130 ft (40 m). Beyond this depth a condition known as nitrogen narcosis (popularly called "raptures of the deep") tends to set in. Caused by the narcotic effects of the air's nitrogen at high pressure, the condition is marked by a loss of judgment that often causes the diver to discard equipment or engage in other dangerously foolish behavior. Nitrogen narcosis also affects helmet suit divers, but not until a depth of about 200 ft (61 m).
|
