The Dark Side of Diving


Night-dives are a great pleasure, but all the more so if they are done right. This month SIMON PRIDMORE turns to developing techniques for optimising your after-hours experience

AFTER A DAY’S DIVING, many people choose to head for happy hour to mull over what they have experienced and exchange notes with other divers. If you postpone the aperitifs for a couple of hours, however, and do a night dive instead, you will find you have a whole lot more to talk about!

When the sun goes down, even a patch of nondescript seabed that seemed boring in the daytime can turn into an underwater wonderland.

It’s a little like Las Vegas – a dull desert town by day but a fantasyland after dark. The marine world is transformed by the many nocturnal fish and animals that come out to play: and everyone gets dressed up for the party!

Daylight denizens of the reef such as triggerfish lock themselves into crevices with their dorsal spines; parrotfish surround themselves in a mucus bubble and the bizarre creatures of the night go out on the prowl.

Nudibranchs, crabs, lobsters, octopuses, brittlestars, urchins and other weird forms of life hunt, mate and feed all over the place! Coral polyps spread their glorious tentacles and plankton erupts in incandescent bioluminescence, illuminating the scene.

To participate in this bacchanalian orgy you just need to plunge in, take it easy and take it slowly, but some tips and tricks will come in useful as well. So be sure to make the right night moves.

Don’t carry a camera until you have mastered the key night-diving skill combination of using a torch while maintaining neutral buoyancy and keeping track of where you are. Dive the site during the day first. It will make natural navigation much easier.

Dive with your regular team, rather than strangers. Make sure you agree on the plan for the dive in advance. Stay close and keep the beam of your partners’ lights in your peripheral vision or look up and check frequently.

Night-diving is not an exercise in swimming great distances or moving quickly. It is all about staying still, concentrating on a small area and observing carefully.

Tell someone where you are going and when you’ll be back. Then stick to the plan, no matter how good a time you are having, to avoid creating undue anxiety or causing them to activate the emergency services needlessly.


  • To ensure that you’re not disorientated, use a downline if you can and descend slowly, feet first, facing the other members of your team.
  • Shine your light downwards and keep fins still so that you avoid touching and disturbing the seabed below.
  • Pause when you arrive at depth, check your buoyancy, and then get yourself horizontal and well-trimmed before moving off. At the end of the dive, ascend via a line or up a wall so that you always have a reference.

Good buoyancy control and minimal finning are crucial ingredients for a good night dive. If you are one of those divers whose feet move when the rest of your body is still, work hard on the under-rated skill of remaining motionless.

During the dive, relax. Adopt a long breathing pattern, taking slow deep breaths.

Check your computer and pressure gauge a little more often than you would on a day dive.


  • Always carry back-up – take three lights with you on every night dive: a primary, a secondary and a marker light.
  • Your main and brightest light is called your primary. To get the most from night-dives, it’s worth investing in a good torch.
  • Choose one with rechargeable batteries, because these are both more cost-effective and more eco-friendly.
  • Many good lights have variable settings so that you can adjust the level of brightness. If your light is too bright you risk scaring away the very animals you are trying to see.
  • You want a floodlight rather than a spotlight, so that you can bathe a larger area in a smooth, featureless pool of light without filament or reflector shadows.
  • Ensure that the burntime is more than adequate for the planned length of your dive, plus a few minutes before and after.
  • Lights with a one-finger on/off switch are much easier to use than those that are activated by twisting the lens cover, as you may not always have two hands free.
  • See that the light has a wrist lanyard, because most lights are negatively buoyant and you don’t want to lose it if you find you need your light hand for something else in an emergency.
  • Your primary light should also have a metal clip so that you can attach it to a D-ring on your BC should you need to switch to your secondary.
  • Your secondary light is not a luxury. Sooner or later, your primary will fail during a night-dive, and when it does, your secondary has to provide the illumination required for you to terminate the dive, ascend, and leave the water safely. Don’t be tempted to continue the dive using your secondary, because you no longer have a back-up if it fails.
  • As with the primary light, you want a good-quality secondary that’s dependable. It should be smaller than the primary, because it needs to be stored on your harness or in a BC pocket. A great idea is to use the torch you normally carry on daytime dives as your secondary light.
  • You wear a marker light not so that you can see but so that you can be seen, both on the surface and under water, and from all directions at all times. Tie it to your cylinder valve or attach it to your BC shoulder harness.
  • Switch it on before you enter the water, and leave it on until you’re back on the beach or boat.
  • Chemical light-sticks are the most popular choice of marker light. They are cheap and disposable, but even though the latest models contain reef-friendly liquid they still need to be disposed of responsibly.
  • Battery-powered marker lights are more expensive but are reusable. The best of these also have a strobe mode in which you can set an optional flashing sequence. This conserves battery power and makes you more visible to searchers if you are drifting at night.


  • Always switch your primary light on before entering the water.
  • If entering the water via a giant stride or backward roll from a boat, protect your light to keep the impact to a minimum. Once you’re in the water, check that it’s working before descending.
  • Once you have your light deployed and spot something cool, use the edge of the pool of light (not the centre of the beam), to illuminate it so that you don’t scare it or blind it.
  • Don’t turn your light off and back on under water. This just increases the likelihood that it will fail.


  • The most effective way to attract the attention of your partner on a night-dive is to shine the beam of your torch into the pool of light thrown by their light, and move it around.
  • Once you have their attention, make a slow circle to ask “OK?” or move the light swiftly from side to side if you have a problem. Shine your light onto your free hand to illuminate hand signals.
  • Never shine your light into a fellow-diver’s face. You may not get the friendliest response as they struggle with having been temporarily blinded.
  • On surfacing, avoid pointing your light directly at the boat. The crew-members need their night vision.


  • If boat-diving, ensure that there are marker lights positioned both on the boat, and at the top and bottom of any descent-line. The lights should be on before the dive begins and left on until every diver has successfully returned and been accounted for.
  • If diving from the beach, shore-lights are valuable reorientation tools. They should be of sufficient brightness that they can be seen from the sea even if rain or mist comes up during the dive.
  • Two or more shore marker lights can be used, one above and behind the other, so that divers returning on the surface can navigate back to their starting point by aligning the two lights.

Embrace night-diving; develop your skills; get the right lights and get your lights right!

Read more from Simon Pridmore in:
Scuba Confidential – An Insider’s Guide to Becoming a Better Diver
Scuba Professional – Insights into Sport Diver Training & Operations
Scuba Fundamentals – Start Diving the Right Way

All are available on Amazon in a variety of formats.



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