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Night dives are great fun and you see a different underwater world at night. This article explains the additional considerations that are required at night.
Introduction
Night dives can be great fun, but they're not without risks. If your diving abroad make sure that all divers are fully aware of the additional risks associated with dangerous creatures, for example, Sharks and Lion fish are much more active at night.
Ensure the following conditions are met:
- Good weather.
- Good surface visibility, don't dive in fog, heavy rain etc.
- SMB's should have lights, strobe or light sticks on.
- All divers to have main and backup torch.
- A restricted diving area.
- Minimal accidental penetration risks.
- Exit points are lit with coloured lights (to distinguish from other lights).
Night vision
Before getting on-site, warn about night vision. It takes at least 15 minutes of near-darkness for our vision to adjust to low light. A torch beam shone in the eyes, or car headlights can destroy night vision for another 15 minutes. Advise that all divers check torches before kitting up and turn headlights off and use dim light while getting ready. When ready to dive, eyes will be well adjusted for night vision.
Torches
Divers should have two torches each, one main and one backup, Avoid head-mounted torches on night dives as one glance at your buddy destroys their night vision. On the dive, never turn torch out, as the bulb is most likely to blow when turned back on. If want to black out torchlight (e.g. to see photo plankton flash), put torch head against body or cover with hand.
If the torches have rechargeable batteries, make sure they are fully topped up. If they're disposable, put a fresh set of batteries in regardless.
Signals
Reiterate torch signals. Signal with the beam on the seabed where your buddy is looking, not in face. Common signals include:
- Rapid side-to-side movement underwater = attention, look this way.
- Rapid side-to-side movement on the surface = problems come get me.
- Slow large circle = OK (like finger and thumb circle).
- Steady beam straight up at surface of water - alarm to surface cover (most torches balanced to do this if let free for this reason).
- When giving hand signals, shine torch at your hand so buddy can see it (tricky if two-handed signal - tuck torch under arm).
- It is important for buddy to confirm signal by repeating it as it is easy to misunderstand in dark.
Buddy checks are important as it is easy to miss things at night. Go through the checks religiously and test things work properly. On the dive, pay special attention to navigation as there are less cues than with sunlight. It is easy to get disorientated and to go deeper than you intended as you loose the normal darkening cues that you would get in the day. Watch your depth gauge often and check buddy is too. The same lack of light cues, make it easier to go inside things like wreck or caves without realising. Shine torch all around regularly to check.
After dive and de-equipment, make special torch search of whole area to ensure nothing left behind.
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