If you are diving inside an unlit wreck or at night, it’s pretty obvious you’re going to need some form of light and there’s a plethora to choose from. What may not be so obvious is that if you are diving in water under bright tropical sunshine, everything will look monochromatic thanks to the fact that water selectively filters the light so that more than a few metres away from the surface, everything looks blue. Not only that, but try looking under ledges for any animal that might be lurking there (and that’s where a lot of animals lurk during the brightest part of the day) and everything gets lost in deep shadow.
So in actual fact a powerful diver’s light is just as useful during daylight hours as it is when there is no natural light by which to see your way. The difference between having a weak light and no light at all is clearly obvious too at night, but during the day you’ll need a light that can compete with the daylight, filtered as it is by the water. That’s why you’ll see successful underwater photographers using powerful underwater strobes to light up their subjects and videographers often using powerful video lights.
Years ago, underwater lighting was limited by the size of the battery that could fire up a conventional halogen lamp. Powerful lights tended to be both huge and heavy. More recently, lithium-ion battery technology combined with modern LED bulbs can give us a powerfully bright light with a useful burn-time combined in a compact package.
A good example of that is the Nanight Sport dive torch. This Swedish torch uses a cluster of three Cree XM-L2 U2 LEDs in a single module to push out up to a massive 3000 lumens fired up by its lithium-ion battery pack and the beam so produced can either be a narrow 12° suitable for those diving in low visibility conditions and who want a tight penetrative beam, a 35° beam that is generally very useful, or a wider 55° beam for those diving at night who may be a little nervous about what might be close by but not immediately lit up. It’s important to choose the appropriate one for your needs.
For example, I took a torch limited to a narrow beam on a trip to dive the wrecks of Truk Lagoon. It was a mistake. Swimming about inside the engine rooms and holds of these 1944 relics from the Pacific War, I missed a lot of details because the beam was too selective. The next time I went I made sure to use a torch with a wide beam and missed nothing.
The burn-time at a full 3000 lumens is a little under one-and-a-half hours, which is more than enough for any daylight dive when you might need the maximum intensity, but you can progressively dim it in four stages and the burn-time increases pro rata. This is effected by a magnetic switch that functions sequentially and a micro processor controls the light intensity. If you are worried that the light might overheat, the LEDS are temperature monitored.
You might find that 750 lumens is quite enough once your eyes have adjusted to the darkness and should you be doing a series of leisure dives on wrecks, there will be more than enough power in the battery for a full day’s diving, with some to spare. You’ll only need to recharge the torch once each day.There is a battery charging indicator that turns from red to green as it is charged. Recharging from flat takes a few hours and before the light extinguishes due to low battery power it continues with progressively lower light output. That equates to something of a get-you-home mode.
All this technology is contained within a tube that is around 15cm long and 5cm in diameter. It weighs a mere 500g and is depth-rated to 100m, which is enough for most people! When you first switch it on, it flashes up to four times to indicate the state of battery charge.
If you want an even longer burn-time, the Nanight Tech dive torch uses a similar head that is powered via an umbilical by a larger 20cm long battery pack and weighs around a kilogram. It will run for two-and-a-half hours at full output with an extra hour with gradually reducing light output. The battery canister attaches to your tank, backplate or other convenient place and the head, only 8cm long, is supplied with a Goodman handle that allows hands-free use. It comes with the two reflectors for the narrower beams.
One last point: When using extremely bright lights like these, avoid shining them towards the eyes of other divers. If you wish to signal, point the light at your signalling hand.