UNDERWATER lighting is almost essential when diving in murky British waters, and it is also handy at the surface to help the cover boat locate you. In clear tropical waters, a powerful light enables a diver to see marine life in its full glory.
Underwater lights vary from the smallest mini torch like the Teklite Microlite, powered by a single AA dry cell, to enormously powerful super-troupers fired up with huge lead acid batteries, like the RoHo HP Lantern. In between are bright torches such as the Ikelite PC and popular lanterns such as the UK400 and Tec4000, which use dry cells or rechargeable ni-cad batteries.
Dry cells tend to give several hours of burn-time, so a couple of sets can provide a whole week's diving in a remote location. Ni-cads provide plenty of power for a brighter light but need to be re- charged between dives. A ni-cad-equipped lamp can be recharged almost ad infinitum, provided you have the electricity supply needed, but buying a ni-cad involves a greater outlay of money at the time of purchase.
A new style of light has now been developed that was originally designed for technical and cave divers. A large and, by necessity, heavy power-pack is attached to the diver's tank, BC or belt, and replaces the equivalent weight in lead.
Power is fed to a small yet powerful lamp-head by an umbilical lead. More than one lamp can be supplied and these can be mounted on the head or wrist of the diver to achieve hands-free operation. Examples of these are the DiveRite MLS MR16, the Metalsub KL 1255 and the very popular (and lighter-weight) NiteRider series.
Finally, there are underwater flashing beacons. These use a normal torch-like bulb and circuitry to make them flash intermittently, or an electronic discharge tube like that of a small camera flash, which fires continuously. They are useful as emergency signals and for attaching to a marker buoy for use at night.