Monthly Archives: June 2012

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How to Use Natural Navigation When Scuba Diving and10 tips for improving your underwater navigation skills.

English: Photograph of certain underwater navi...

English: Photograph of certain underwater navigation tools (Photo credit: Wikipedia)

 

 

 What is Natural Navigation?:

Natural navigation is a technique for orientation in which a diver uses features of the underwater environment as directional cues. Navigating your way underwater where there are no roads, no signs, no prominent landmarks so to speak is not an easy  Scuba diving skill to master. Coupled with other factors playing on a divers mind like buoyancy control, keeping time, depth, conserving air and of course co-coordinating with your buddy, underwater navigation is all the more difficult to keep a track off.  Dive sites don’t come with maps and the terrain underwater appears random, irregular and often unpredictable unless you’ve dived the site before a number of times, so this diving skill takes more than a little practice to acquire. Successfully navigating using natural features takes some practice, but is worth learning. Divers must develop situational awareness, consciously observing and taking note of the underwater features around them. Situational awareness may sound easy – what can be simpler than looking around? Yet, the underwater world is filled with so many beautiful distractions (turtles, rays, coral, etc) that it is easy for a diver to lose himself in the details. Divers (especially new divers) are task loaded underwater. Monitoring depth, dive time, buoyancy and tank pressure consumes attention that could otherwise be used to keep track of surroundings. Navigating by natural navigation requires forethought and a conscious decision to pay attention!

Natural Navigation Begins Before a Dive:

The first step in successfully using natural navigation to traverse a dive site is to become familiar with the features of the dive site before entering the water. Decide on some basic landmarks or cues to use for natural navigation based on a map or dive briefing. Once underwater, a diver simply confirms information that he already is familiar with to navigate the dive site. As an example, a diver may view a map of a coral reef before a dive and decide to swim out against the current with the reef on his left, and return to the boat with the current with the reef on his right. Once he has agreed on this course with his buddy, maintaining orientation during the dive becomes easy.

Depth:

A good diver is always aware of his depth during a dive, but not all divers (even great ones!) realize that depth can be a powerful navigational tool. Many dive sites near shore have a gently sloping floor that deepens as the diver moves away from land. A diver who swims progressively deeper along the bottom knows that he is moving away from the shore, and a diver who swims shallower will realize that he is swimming closer to the shore. If a diver’s depth does not change, chances are that he is swimming parallel to shore. Of course, this is not always the case, and depth changes for a given dive site may vary. A diver should familiarize himself with expected depth variations for a dive site before entering the water.

Structures and Topography:

Perhaps the most obvious form of natural navigation is navigation by underwater features such as reefs, shipwrecks, walls, and other structures. A dive site map is incredibly useful in determining the layout of a dive site and choosing which features to use as navigational tools before a dive. As an example, the map may indicate a coral reef with an edge along a sandy bottom. Decide where to swim in relation to this edge before the dive. Similarly, a diver who plans to dive shipwreck may decide on his route over the wreck ahead of time using structures and features of the wreck. Slopes, dunes, coral walls, and artificial features such as mooring hooks and man-made debris make great references for natural navigation. In the worst case scenario, a diver without a map can make a quick plan by floating on the surface in clear water, observing the reef, and agreeing on a plan with his buddy before the dive.

Current:

A constant current may provide a sense of direction underwater – but be warned currents occasionally shift. Divers who use current to provide a sense of direction should begin the dive by swimming against the current and end the dive by swimming with the current. A diver who attempts to swim perpendicular to the current will find that it pushes him away from his original course. He may have difficulty returning along the same route. If using current as a natural navigation tool, be sure to use back-up references, such as depth and structures, in case the current shifts direction.

Sand Patterns, Sun and Shadows:

In dive sites with water movement, ripples may form in the sand. These patterns generally run parallel to shore, and can help to provide a directional reference. During morning and late afternoon the position of the sun (and the shadows cast by the sun) can provide an additional reference. Of course, this doesn’t work around midday, when the sun is directly overhead, or on very long dives during which the sun may change position.

Reference and Look Behind You as You Swim:

Divers with good situational awareness use a combination of many of the above navigational techniques to maintain orientation during a dive. However, remember that your chosen visual references may look unfamiliar when viewed from the opposite direction upon return. Periodically look back at the return path to create a series of mental “snapshots” which will help you recognize you return path.

 

10 Tips for improving your underwater navigation skills:

 

1.      Plan Ahead

An important part of underwater navigation is gathering as much information about the location before hand. Collect information about the expected scenario like large coral formations, rocks, drop offs, sandy patches, wreck size, and so on from experienced divers or dive operators in the area.

2.      Draw a Map 

Map out the dive site on dive slate before you go and maybe chalk out an intended dive plan in the direction you want to go in for reference underwater. Sometimes just doing that helps you visualize the map in your head and you may not need to use the map. A good idea is once you’re diving the site you can note certain landmarks on your map to find your way back easily.

3.      Know where your dive boat is

Just like a car in a parking lot you need to make a note of where your dive begins, so as to return to the right spot. Make a mental note of the surroundings, any particular rock or coral formations where you first descend. Pay attention to the direction you can see the sun and remember what your dive boat looks like from under especially if there are more than one in the vicinity.

4.      Carry a compass

As a minimum, a diver must carry an underwater compass for navigation. Buy a simple compass and learn the correct way to use it. Take it on guided dives to get the hang of using it before heading off on your own.

5.      Setting the bezel

Before beginning a dive you should set the bezel of your compass to point you to the direction dive boat and in case of shore diving to the shore. In this case once the bearing is set it shouldn’t be changed during the dive and to return, one simply rotates himself in the opposite direction.

6.      Measuring distance

A rookie mistake when it comes to underwater navigation is noting down the direction but completely losing track or not measuring distance. It’s important to know exactly how far you have swum out and in what direction in order to return. One way of doing this if you are a consistent swimmer is by time or even air consumption. It may not be as accurate as counting fin strokes as you are thought in your course but it sure beats spending most of your dive concentrating on counting rather than the surroundings.

7.      Use natural directional indicators

When diving in good clear water conditions and in the day, the sun is a great natural compass. For example during a morning dive you know the sun will be in eastern direction while for afternoon dives the sun indicates west.Sand ripples caused by currents too are good directional indicators as they always run parallel to the shore. The deeper imprint of the ripple, the nearer to the shore you are.

8.      Don’t use currents as indicators

Don’t rely on currents to tell you in which direction you are heading. Currents can twist and turn around undersea objects thereby leading you astray.

9.      Trust your instruments

If there is a discrepancy between what you feel and what your dive compass is telling you, go with the compass. Be sure that it is working properly before the dive and that there is no interference from undersea objects like shipwrecks or anything that can be magnetic however.

10.  Practice

Practice using your compass on land. Do squares, rectangles, set headings and reciprocals, note bearings, in short perfect your compass skills on land. Then on guided dives, practice your own navigation rather than blindly following the dive master, it’s a great feeling to successfully hit your mark when you try. Make it a habit to jot down things like bearings, landmarks, directions, times on your dive slate throughout your dive. With time and practice you’ll be a pro at navigating during a dive and even the fish will be seeking your instructions.

 

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What is Deep Diving?

Dive in places where only a few have explored before!

New divers will usually feel a mixture of excitement and fear at the thought of doing a deep dive. Deep diving can certainly be exciting and it’s definitely healthy to maintain a certain level of caution as well. Depth attracts a lot of divers as deep dives provide this certain kick.

Get the experience of diving on a wreck below 100 feet/30 meters!

To do these dives safely, you need the right skills and the right knowledge .

Without proper training this kind of diving is an uncontrollable safety risk. To plan your dives properly you must first know about all of the potential risks involved in DEEP DIVING.

How Deep is Deep?

Different divers have different ideas about when a dive is considered a deep dive.

The meaning of the term deep diving is a form of technical diving. It is defined by the level of the diver’s diver training, diving equipment, breathing gas, and surface support.

In recreational diving, PADI define anything from 18 metres (60 ft) to 30 metres (100 ft) as a “deep dive” (Other diving organisations vary)

In technical diving, 60 metres (200 ft) may be a “deep dive”

In surface supplied diving, 100 metres (330 ft) may be a “deep dive”

To put it in perspective, an Open Water Diver is certified to dive to 60 feet / 18 meters and an Advanced Open Water diver is certified to dive to 100 feet / 30 meters.

The limit of recreational diving is considered to be 140 feet / 40 meters and this is the depth that a diver trained in deep diving is certified to descend to.

Usually, a deep dive is considered to be a dive between 100 feet / 30 meters and 140 feet / 40 meters.

Why Dive So Deep?

The main reason to dive deep is to see things that you can’t see at shallower depths. It’s quite common for well preserved wrecks to be found in deeper water, as the greater depth means less exposure to surface surge.

You will also find that different marine life exists at different depths. On tropical reefs it’s common to find healthier coral at greater depths due to less exposure to the sun and to divers. Many fish and other marine creatures also prefer greater depths.

Of course a disadvantage of diving deeper is less visibility and color due to less sunlight. Many divers will carry a dive light to bring the color back to coral and it is necessary to use strobe lighting for photography at any depth greater than 15 feet / 5 meters and particularly on deep dives.

Deep Diving Concerns

Like most types of recreational diving, deep diving is very safe as long as the proper precautions are taken. The main concerns in deep diving are increased chances of decompression sickness, rapid air consumption, and nitrogen narcosis.

Decompression sickness

Due to increased pressure at greater depths the chances of decompression sickness are increased. This can be countered by properly planning the dive using dive tables or a dive computer and ensuring that you ascend slowly and complete all necessary safety or decompression stops. Some divers believe performing deep stops in addition to a normal 3 minute safety stop will decrease their chances of suffering from decompression sickness.  Decompression sickness, or the “bends”, can happen if a diver ascends too fast, when excess inert gas leaves solution in the blood and tissues and forms bubbles. These bubbles produce mechanical and biochemical effects that lead to the condition. The effects tend to be delayed until reaching the surface. Bone degeneration (dysbaric osteonecrosis) is caused by the bubbles forming inside the bones; most commonly the upper arm and the thighs.

Air embolism causes loss of consciousness and speech and visual problems. This tends to be life threatening, and requires a recompression chamber for treatment.

Deep diving involves a much greater danger of all of these, and presents the additional risk of oxygen toxicity, which may lead to a convulsion underwater. Very deep diving using a helium–oxygen mixture (heliox) carries a risk of high pressure nervous syndrome.

  

 

 

 

 

 

Decompression stops

Using normal scuba equipment, breathing gas consumption is proportional to ambient pressure – so at 50 metres (160 ft), where the pressure is 6 bar, a diver breathes 6 times as much as on the surface (1 bar).

Heavy physical exertion causes even more gas to be breathed, and gas becomes denser requiring increased effort to breathe with depth, leading to increasing risk of hypercapnia, an excess of carbon dioxide in the blood. The need to do decompression stops increases with depth. A diver at 6 metres (20 ft) may be able to dive for many hours without needing to do decompression stops. At depths greater than 40 metres (130 ft), a diver may have only a few minutes at the deepest part of the dive before decompression stops are needed. In the event of an emergency the diver cannot make an immediate ascent to the surface without risking decompression sickness. All of these considerations result in the amount of breathing gas required for deep diving being much greater than for shallow open water diving. The diver needs a disciplined approach to planning and conducting dives to minimise these additional risks.

Due to more rapid air consumption at greater depths it is important to closely monitor air gauges ad to allow a greater air reserve at the end of the dive. It is also recommended to make use of a redundant air source in case you become low on air. This means either carrying an additional small cylinder of air called a pony bottle or having a drop tank available. A drop tank is an additional cylinder with an attached regulator that is hung from a rope off the dive boat. It is normally hung at 15 feet / 5 meters, so that it is easily accessible during safety stops.

Nitrogen narcosis 

Nitrogen narcosis, the “narks” or “rapture of the deep”, starts with feelings of euphoria and over-confidence but then leads to numbness and memory impairment similar to alcohol intoxication.

The air we breathe is constituted of 79 nitrogen, an inert gas that has no effect on our bodies under normal surface pressure. However, as we descend into the water the increased pressure increases the partial pressure of the nitrogen, which means that it has the same effect as breathing greater concentrations of nitrogen. This increased nitrogen affects the synapses in our brain and brings on a feeling very similar to drunkenness. Nitrogen narcosis becomes noticeable to different people at different depths, but begins to affect most people at around 50 feet / 15 meters. The first effects are normally tingling of the fingers, followed by slow thinking, dizziness, disorientation, and impaired decision making. Most people report feeling the effects of nitrogen narcosis at depths greater than 100 feet / 30 meters. The deeper you go the greater the effects. Nitrogen narcosis poses no long term health risks and all symptoms are relieved as soon as the diver ascends. It is recommended that dive buddies monitor each other for symptoms of nitrogen narcosis and ascend to avoid severe narcosis.

Coping with the physical and physiological stresses of deep diving requires good physical conditioning

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