A diving torch or lantern is an essential item of diving equipment whenever underwater light conditions are poor. For night diving, obviously, it is one of the important items of equipment, but it can also be very useful on other occasions for looking into confined spaces in rocks, wrecks, etc.
A diving torch or lantern can vary considerably in size and power. It may use standard batteries or rechargeable cells. The advantage of rechargeable cells is that operating costs are reduced, but a source of mains or 12-volt (car battery) power is needed for recharging. With the advent of halogen bulbs and small powerful batteries it is possible to have a quite small underwater torch with remarkable brightness. Whether the torch should have a pinpoint beam or a wide-spread one is usually determined by the use to which it is to be put.
Underwater photographers often use a small, pinpoint beam to help aim their cameras and flashguns. The colours that are filtered out by the water as the diver descends will return as soon as the torch is switched on, and for this reason many divers carry a torch on every dive.
