Sign up for a Night and limited visibility course at your local SDI dive center soon to take a dive on the dark side.
What’s the best way to dive the Blue Heron Bridge? Here we outline a few suggestions to ensure an enjoyable dive adventure.
Whenever we talk or think about low visibility, we almost always think in terms of a night dive. This makes perfect sense, but not when we are planning a technical dive. Technical dives have many aspects to consider; first and foremost being the appropriate gas to breathe if we are going to deeper depths or the right amount of gas if we are planning a longer dive. Whatever the technical dive is, preparing as if it were going to be a limited visibility dive should always be part of the planning phase.
Limited visibility comes in all shapes and sizes: reduced light due to depth, limited light due to overhead (wrecks) and no light due to overhead (caves). Each of these factors requires slightly different considerations and all should be considered limited visibility diving. There are some other factors that can turn what should be a good visibility dive into a limited visibility dive. When diving in wrecks exhaled bubbles can dislodge silt, rust or fragile building materials from the ceiling of the wreck. There are also the times when divers in front of you kick up silt in both wrecks and caves which can sometimes bring a dive to no-visibility.
One of the key objectives is that you never get lost, and the same goes for your buddy or team. There are many ways to maintain contact with others underwater and to perform underwater navigation so you don’t get lost. Dive lights allow you to stay in contact and communicate with others on the dive team, reels allow you to run a line leading back to the exit point and, when not around ferrous metals, a compass will do the trick. If the dive is or becomes a limited visibility dive, your options are reduced. Any time a diver is in an overhead environment, wreck or cave, they should also have a line that leads them to the exit point and contact with the line should always be maintained.
With minimal additional equipment and very little additional dive planning, limited visibility diving can be accomplished. Some of the best dives can be performed in limited visibility and for some sites, limited visibility is the best it will ever get.
For more information on limited visibility diving or to locate an dive center in your area please visit us at /sdi/get-certified/Night-Limited-Visibility-Diver/
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Diving at night is one activity that puzzles many new divers, and certainly baffles those who are just thinking about becoming divers. “Can you do that?” “Is it safe?” “Is there anything to see?”
All good questions, and all have similar answers that boil down to “Yep!” And for many of us, the real question is not so much can you do that, is it safe and is there anything to see, but more likely when can we go again?
One of the lures of night diving is that many underwater animals are hidden during the day and only come out to feed and generally interact with their environment at night. Many true fish, invertebrates, crustaceans and mollusks are night-shift workers and, in some area, darkness brings out species that cannot be seen at any other time of day. Even those species that do show themselves in daylight have unique nighttime behavior.
Although visibility under the water is obviously restricted by darkness, night diving does not present the same challenges as diving in low-visibility situations where silt and other particles suspended in the water limit a diver’s visual field. Typically night diving locations – those spots famed for this type of diving – have very good water clarity, and this is heightened by the field of vision being concentrated into the cone of light from the diver’s light. The dive light enables the diver to focus his attention on the objects that his dive light illuminates. Everything else tends to disappear. It’s a fascinating change of perspective that seasoned night divers find really appealing.
In short, night diving can provide a truly unique and extremely rewarding experience; however, to be done correctly, a night dive needs to be properly planned and organized.
As with other types of dive plans, all the normal guidelines should be followed. In addition, there are a few other tips that will help to keep everyone safe and sound.
One of the major issues is that contact and communication between divers and their mates back on the surface, can be challenging. These issues demand special planning and equipment. A lost dive buddy is never fun but on a night dive this situation can be even more distressing. Potentially more challenging is buddy separation combined with disorientation and loosing track of the safe exit point location.
But before we touch on some of those issues, something worth considering is the timing of a night dive. Twilight is a favorite time to start a night dive. For one thing, ramping up for a dive when there is sufficient daylight to see clearly and not trip over gear and rocks and so on is a real bonus. And even though there may be sufficient light on the surface, the low-angle of a close to setting sun does not penetrate the water well and ambient light on the coral or seabed is much weaker than at mid-day or in the afternoon. The marine nightlife kicks into gear before it is fully dark on the surface. Bearing this in mind, some night diving starts and finishes while there is still enough light on the surface to gear up and to make post dive “recovery” simple.
For a really one-of-a-kind dive, plan a “dawn” dive. That’s to say, begin your dive 30 or 40 minutes BEFORE the sun comes up, and watch the change of shifts as the daylight creatures wake up and start their activities and the night owls turn in for the day.
Even if you have planned a “total” night dive, there is usually some ambient light. Jetties, quays, beachfront properties, street lights, even the lights on a dive boat can supply a surprising amount of light when shore or boat diving at night.Also, a full-moon can be a major illumination source. But perhaps the best and most fascinating light supplied by something other than underwater dive lights is bio-luminescence. This is the eerie and colorful light triggered when water filled with phosphorescent plankton is disturbed making these tiny creatures give off a remarkably strong and powerful glow.
Of course, a correctly equipped night diver takes his or her own light source. In fact, a primary light and at least one back-up light per diver. A proper dive light allows a diver to see clearly underwater. The scenery literally comes alive because animals and plants that look blue or black in ambient daylight show their real colors. Modern dive lights are powerful, produce a full-spectrum white light, and are becoming more and more compact every year. Many of the more expensive models have rechargeable batteries but there are really serviceable lights that produce several hundred lumens for several hours with user-replaceable AAA and AA batteries that can be purchased around the world.
Dive lights also serve as a primary tool for communications on a night dive. The glow from a buddy’s light helps divers to keep track of each other at depth. Communication between divers is easy when they shine their lights on their hands and use normal diving signals.
A light can also be used to get your buddy’s attention. While care should be taken not to shine your flashlight into your buddy’s eyes – since this will spoil their night vision for some time – moving a light from side-to-side or up and down, or covering and uncovering the light can all signal to a buddy to look your way.
Buddy lines can be used on night dives, but with decent visibility, buddy awareness and some simple ground rules learned in an Night Diving Program, they should not be required. With a little care and practice, buddies can keep tabs on each other by watching for their lights.
But what happens if a light fails during a dive? This is one reason night divers are advised to carry a backup dive light and at that point to signal their buddy and terminate the dive.
Flashlights are also useful when “communicating” with the surface. All night dives should be conducted with at least one person topside, whether diving from a boat or from shore. The simple reason for this is that they can help illuminate the exit, and can signal to divers if they surface well away from the designated surface point. The surface support is also where a dive plan is “filed” so that if something goes awry, they can immediately summon help.
When the wind is calm and the surface flat – the suggested conditions for night diving – voice communication on the surface is quite effective too.
When shore diving, it is best practice to arrange lights so that from the water, they indicate to divers exactly where to come ashore. This simple solution is the easiest way to make sure that divers do not get lost or disoriented when their dive is over.
The perfect site for a night dive is a sheltered bay or cove that provides easy navigation and facilitates entry and exit. The site should not be deep, and MUST be a site that divers have familiarized themselves with in daylight. One of the coolest things to do on a night dive is to compare what’s seen and what is going on with the same area during the day.
Try it… chances are you will love it!
REMEMBER THE BASICS:
- Night diving offers divers a remarkable challenge and unbeatable fun as long as it is conducted within some common-sense rules.
- Choose a familiar site that is sheltered and shallow.
- Start at twilight. Gearing up is easier when there is daylight to work with. As the light drops when you are underwater, you’ll gradually become acclimated to the ambient light levels.
- Plan short, shallow dives, and be conservative with gas needs. Night divers generally use more gas on night dives.
- Carry at least two dive lights, a primary and a smaller backup.
- See and be seen. Reflective tape on tanks will help your buddy pick you out if there are several divers in the water. Glo-sticks (chemical lights) have fallen out of favor because of environmental concerns, but there are several manufacturers who make a battery-run alternative. Small compact and low-lumen, these are a great aid to divers who are a little nervous about losing touch with the group or their buddy.
- Use basic navigation aids… natural and man-made.
- Have someone on the surface to help when the dive is over and file a dive plan with them so that they know when to expect you back.
Sign up for your SDI Night Dive Specialty by visiting your local SDI dive facility.
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