A true story: A group of divers on holiday on the Great Barrier Reef, Australia camping on the beach for ten days decide its time to go for a night dive. So the buddies all pair off and two recently qualified divers agree to dive together, to allow the rest of the group who are far more experienced to enjoy themselves without worrying about them.
So off they go on a shallow beach dive, conditions are ideal and they are starting to enjoy themselves, when a new divers worst nightmare happens – a shark appears. No, it’s not a Great White or Tiger shark, but a medium sized reef shark. What do they do?
Well about an hour later, the rest of the group emerge and find the two divers fully clothed around the fire enjoying a cold beer. After relaying their brush with death, the question was asked, "Well, what did you do?"
Their answer was simple, "We turned off our torches. If we couldn’t see the shark, it couldn’t see us."
It is the sort of Murphy’s logic that, to this day, you cannot argue with.
For those who have never breathed underwater at night, it is…as they say,"You don’t know what you are missing." But as with anything with scuba – a couple of tips and hints can make the difference between a pleasurable experience and a nightmare. So this month, ten tips for getting your nitrogen fix after hours.
Do not dive a site that you have not dived before. In fact a great combination is a double dive whereby you dive the site in the late afternoon and then do exactly the same dive again when it’s dark. The advantage is that you are comfortable with the site, have some bearings and you are familiar with the entry and exit procedures, especially if you are doing a shore dive.
Start your dive when it is becoming dusk and you will experience the light gradually diminishing; its rather like turning down the dimmer instead of suddenly turning the light off. It is far less stressful and thus your air consumption will be better.
If you are gearing up and it’s already dark do not waste your dive torch batteries to gear up with. To improve your night vision, try gearing up with red lights only, this causes the pupils to enlarge, which maximize your night vision.
To read gauges at night, hold your torch on the gauge for a couple of seconds and then read the gauge, most gauges are luminescent. Dive computers and digital gauges require torches to be held on an angle. If you are considering purchasing a new computer or gauges, look for one that has a built-in light.
Practice adjusting buckles and gear, with your eyes closed during a day dive. Get used to finding and solving problems by touch and feel, so if all fails at night you know that you can solve these minor problems before they become major ones.
Do not shine your torch in your buddy’s eyes. Always point your torch at your own chest when displaying hand signals. However, due to the lack of ambient light, night diving generally is limited to three basic torch signals:
- Moving the torch in a circle…indicates everything is okay
- Moving the torch from side to side…used to gain attention
- Moving the torch up and down…indicates that assistance is required
If possible, when descending use a reference line to avoid disorientation and if you intend settling on the bottom to adjust gear and wait for your buddy. Make sure you check the bottom, what was a desolate sand desert by a mooring buoy during the day can become minefield after hours when sea urchins come out.
At the start of the dive take time to adjust to this new environment. Turn off your torch to see what it is like, so that if your torch fails during the dive you will know how much natural light is available. During a full moon you can sometimes dive using no artificial light.
Trust your instruments and not your instincts; night diving requires far more rigorous checking of your gauges. The darkness can lull you into a sense of complacency and your perceptions of depth, air consumption and time are affected more so than during a day dive. Plan your dive along compass bearings and practice this in your orientation dive.
Just because it is dark does not mean that the decompression demon has gone to bed. Do not forget a slow and safe ascent, with a safety stop. Take the time to prepare for the surface, a safety sausage that allows you to put your torch into the bottom is a great way to signal – you end up with a six foot orange beacon illuminated.
Dive Deep, Dive Safe