# How to predict water visibility for scuba diving shallow water

Sep 26, 2022

## How to predict water visibility for scuba diving shallow water

Visibility is one of the most subjective aspects of diving. Ask 10 people after a dive what they think the visibility was, and you’ll get 9 different answers. The last person will spend a half hour trying to guess.

### Defining

People generally suck at estimating visibility (“viz”). Why is that? I think it comes down to a lack of common definition. I will attempt to define visibility in concrete terms.

The best place to start for this sort of thing is the dictionary. Webster’s defines visibility as

The distance at which something can be seen.

We’re getting closer, but what exactly is the “something” to be seen? I’ve heard a few options: the distance at which hand signals are no longer recognizable, the distance you can’t see a diver’s bubbles, and the distance at which you can’t distinguish an object. The first might be too strict for general use, but the last two start to get the point. Let’s define visibility as the distance at which an object cannot be discerned. The point at which you can’t tell for sure if that is a diver in the distance is the extent of the visibility.

### Measuring

That was the easy part, now comes the hard part. How do we measure viz? Believe it or not, there is an established manner. It requires something called a Secchi disk. The disc is attached to a line and gradually moved from the measurer. The distance where the disk cannot be seen is recorded, with the length of the line being the visibility. Even more advanced methods with higher precision exist using photometers.

That’s nice for Jacques Cousteau, but not for Joe Diver who doesn’t have a Secchi disk on hand.

First of all, don’t feel bad. Viz is hard to guesstimate, but gets easier with experience. Even then, in general a range is a better indicator for estimating viz rather than a hard, fixed number. Try to get the lower end where things get blurry and the upper end where things can no longer be seen. As you get better with distances, this range will get smaller and the “true” viz will probably lie somewhere in between.

One rule with measuring viz for scuba: it measures horizontal distance. Vertical distance can be deceiving, as light from the surface increases visibility. However, it can be useful both for an upper bound on your range (vertical viz will always be higher than horizontal) and for estimating distances, since you always know your depth. Some, as a rule of thumb, define the viz as the vertical visibility (the depth where you can no longer see the surface) minus 3 m / 10 ft. Probably a good guideline, but useless in most of the tropics, where the viz always exceeds the dive depth.

Try to use anything you have to your advantage. Length of a wreck, for instance. You can find this out easily and use it to gauge distances more accurately.

### Utilizing

I’ll let you in on a secret: it doesn’t really matter. Viz is cool for bragging (“We could easily see over 100 meters!”), but there aren’t too many practical reasons where an accurate number is necessary. There are exceptions, however. For instance, a photographer probably cares more so than others, since the equipment they take can depend on these numbers.

In general, ranges are fine, and even broad descriptions sufficing as well. A scale that goes something like amazing -> great -> good -> ok -> where’s my buddy? -> I can’t see my hand, is descriptive and covers most situations. Make an educated guess, compare to the guesses of others to refine your estimation abilities, but don’t get too hung up on the ever-elusive viz.

## Factors Affecting Visibility When Scuba Diving

Natalie Gibb owns a dive shop in Mexico and is a PADI-certified open water scuba instructor and TDI-certified full cave diving instructor.

Put simply, in diving terms, visibility is an estimation of water clarity and is defined as the distance a diver can see horizontally. Many divers abbreviate visibility with the slang term “viz.” Visibility is given in units of distance, such as “50 feet of viz.”

## What Are Factors That Affect Visibility Underwater?

PADI’s review questions from the open water course review several main factors that affect visibility underwater: weather, suspended particles, and water movement. These seem like only one factor to me, as weather causes water to move, which causes particles to float into the water. Here is my list of five common factors that can disturb visibility underwater.

## 1. Particles in the Water

Suspended particles of sand, mud, clay, or other bottom sediments affect the visibility underwater in much the same way as fog effects visibility on land – distant shapes become colorless, poorly-defined shadows. Visibility reduction caused by suspended particles may be slight or severe depending upon the density, type, and amount of sediment suspended in the water. As an example, clay sediment will become suspended easily, will reduce the visibility to nearly zero feet in a few moments, and will remain in suspension for many hours. In contrast, sand does not become suspended as easily as clay, rarely reduces the visibility to zero, and will fall out of suspension in a matter of minutes.

Sediment particles become suspended when they are disturbed by water movement or by divers. Natural causes of water movement that forces particles into suspension include currents, wave action, choppy seas, runoff, and rough weather. A diver can stir up bottom sediments and reduce visibility by using improper kicking techniques, by swimming with his hands, or by landing on the bottom (one of the many reasons these actions are discouraged).

Water of different salinities forms distinct layers in a manner similar to that of olive oil and vinegar. The interface between the two layers is called a “halocline” (halo = salt, cline = gradient). When viewed from above, an undisturbed halocline resembles a shimmering underwater lake or river (an effect caused by the variation of refractive properties with salinity). However, when water of different salinities is mixed, the visibility becomes very blurry. Divers have compared the visual effect of swimming in a disturbed halocline to having lost one contact lens, to being inebriated and unable to focus, and (my favorite) to swimming in Vaseline. The loss of visibility in a halocline may be extreme; a diver can see light but cannot distinguish shapes. In some cases, a diver in a halocline may even have difficulty reading his gauges!

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Haloclines are encountered in estuaries, at springs that empty into the ocean, and at inland caves and caverns. A diver may also observe the blurry effect of mixing fresh and salt water near the surface of the ocean during a rainstorm, as the fresh rainwater mixes with the ocean’s salt water.

To avoid the visual disturbance caused by a halocline, a diver must swim above or below the depth where water of different salinities mixes. Once a diver leaves this mixing region, the visibility clears immediately. If ascending or descending to escape the halocline is impossible, a diver can minimize visual disturbances by swimming to the side of (but never behind) other divers, as their kicks will mix the water and make the visual disturbance worse.

The term “thermocline” signifies a temperature gradient (thermo = temperature and cline = gradient), or a level at which water of two different temperatures meets. Water of different temperatures layers similarly to water of different salinities, although the effect is not as pronounced. Colder water is denser than warmer water and sinks below it. Therefore, divers will typically encounter increasingly cold layers as they descend. When the temperature difference between two water layers is extreme, the interface between the two layers looks “oily” (similar to a halocline). In general, the visual disturbance created by different water temperatures is not great, and a diver quickly passes through the thermocline region as he ascends or descends, hopefully enjoying the pretty visual effect.

## 4. Organic Particles

Bacteria or algal blooms can disturb the visibility in a very dramatic way. A typical place to encounter this sort of visual disturbance is a body of fresh water with little or no circulation. Algae and bacteria usually require very specific conditions of temperature, salinity, and light, and may be present only seasonally. An example is Cenote Carwash in Mexico’s Yucatan Peninsula, where an algal bloom is present only during the warmer months. The algal bloom forms an opaque, greenish cloud extending from the surface to about 5 feet. Divers must descend through the cloud in near zero visibility before reaching the crystal-clear spring water of the cenote. The presence of organic particles may also be indicative of pollution.

## 5. Hydrogen Sulfide

Unless he is diving in a cave or cavern, a diver is unlikely to encounter hydrogen sulfide. Hydrogen sulfide is most commonly found in fresh water with little circulation where decaying organic matter is present. Large quantities of hydrogen sulfide tend to form a dense, foggy layer, as in Cenote Angelita in Mexico. When only a small amount of hydrogen sulfide is present, it forms thin, smoke-like wisps. Inside a cloud of hydrogen sulfide, the visibility is almost zero. Hydrogen sulfide is worth mentioning because the visual effect is fascinating.

## The Take-Home Message About Visibility

Water clarity, or visibility, is affected by a variety of factors. Identifying the cause of a visual disturbance will allow a diver to manage it correctly. Keep in mind that visual disturbances may be caused by factors other than water clarity, such as foggy masks, reduction of ambient light, nitrogen narcosis and oxygen toxicity. The cause of any reduction in visibility or visual disturbance should be identified by the diver, and proper judgment should be used when deciding whether to continue with the dive or not.

## Diving In Shallow Water

Most people believe that diving is only possible in very deep water, however, diving is possible in water as shallow as two feet. There are many different types of diving, each with its own depth requirements. The most common type of diving is scuba diving, which requires a minimum water depth of ten feet. Other types of diving, such as free diving and spearfishing, have different depth requirements.

As a general rule, the maximum depth for recreational diving is 130 feet, but your experience level, training, and diving type will all have an impact on how deep you can dive. The main reason we can only dive at certain depths in SCUBA diving is due to nitrogen (and other gases). To dive to the deepest point, consider decompression sickness, air consumption, and nitrogen narcosis. The deeper you dive, the faster you will breathe in. When oxygen is elevated in air with extremely high partial pressures, oxygen toxicity becomes a concern because it becomes toxic and convulsions are possible. Because each layer of enriched air provides the deepest operating depth, the depth of a dive can be limited. Nitrous oxide, or nave underwater intoxication, can occur when diving deep.

Divers enjoy diving into deep wrecks or other structures found extremely deep under the sea. Technical divers can dive to depths ranging from 130 to 330 feet. Attempting these depths without the necessary certification from the local authority is not a good idea.

PADI Master Divers are qualified to dive to depths of 30 meters/100 feet or 40 meters/130 feet with the Deep Diver Specialty, allowing them to reach a depth of 30 meters/100 feet or 40 meters/130 feet. From the age of 12 to 14, PADI Junior Master Divers can dive to depths of up to 21 meters (70 feet).

A freediver’s dive to a depth of 40 feet (12 meters) is generally considered safe. Your body begins to feel the effects of a lack of oxygen and water pressure as you reach a depth of 60 feet (18 meters). When a swimmer reaches the end of their swimming career, he or she will typically dive to a depth of 20 feet (6 meters).

On Monday, the man broke the Guinness World Record for the deepest scuba dive, diving more than 1,000 feet (305 meters) beneath the surface of the Red Sea.

A Bend or DCS is a phenomenon in which a scuba diver’s breathing air from a scuba tank causes the balance of gases inside the body to shift. The more you dive, the richer the effects will be.

## How Far Can Divers Dive?

Credit: www.diversdock.com

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Divers are able to dive to depths of over 1,000 feet, but most dives are much shallower than that. The record for the deepest scuba dive is 1,044 feet, set by Ahmed Gabr in 2014.

Recreational scuba divers can dive to depths of 130 feet or 40 meters, depending on the depth of the water. Divers in open water can dive to depths of 60 feet. After completing the advanced open water certification course, people are better prepared to dive deeper and more frequently. Decompression stops, navigation, and dive planning are just a few examples of these. A freediver who does not wear scuba equipment holds the world record for freediving at 702 feet. Divers must be at least 200 feet deep in order to consider a deep dive. Divers over 100 feet deep are frequently referred to as recreational divers.

Divers must have the appropriate skills and safety knowledge in order to make good decisions. As you gain depth, the pressure on your body increases as it moves deeper into the water. People who consume a lot of nitrogen may experience symptoms similar to intoxication. During a deep dive, it is possible to use a lot of air at once. As a result, air is compressed and breathes more freely. Tropical coral reefs are the most popular diving locations for recreational divers. If you want to dive wrecks, you’ll most likely want to get some training in deep diving. Recreational scuba divers typically dive depths of less than 60 feet, whereas tech scuba divers dive hundreds of feet.

Divers interested in diving at deep depths usually limit themselves to dives within the recreational diving depth limit of 40 meters, but technical divers will go anywhere up to 50 meters. Because of the longer dives and the specialized gear, technical diving gear is more specialized. There is an argument to be made that the recreational diver is interested in diving to deeper waters, but the gear he is wearing and the length of the swim make diving to depths beyond the recreational depth limit extremely dangerous. When diving with a recreational diver, it is recommended that the water temperature be at least 50-150 feet per minute, with speeds ranging from 0.5 to 1.5 knots (50-150 feet per minute). Divers who are dressed properly and are willing to exceed their own expectations can go up to 18 meters or more in a dive.

## How Long Can You Dive With Scuba Gear?

Credit: Sport Diver magazine

Most scuba diving gear has a maximum depth limit of 130 feet, which is more than enough to reach most interesting dive sites. If you are an experienced diver and are interested in going deeper, there is special scuba gear available that is rated for depths up to 1,000 feet.

The amount of time that a scuba diver can spend underwater varies greatly depending on a variety of factors such as depth, experience, conditioning, currents, previous dives, and so on. A typical scuba diver can stay in the water for an extended period of time, longer than 100 feet. As you get deeper into the tank, you’ll notice that your dive is shorter. Diver A can still reach 1000 pounds, despite his lack of height. Diver A may have had to return to the surface after 35 minutes of diving, whereas Diver B may have had to dive for 20 minutes after 35 minutes. Divers are not only more diverse as a result of these factors, but they are also more likely to be in different states of mind. The more you dive, the more comfortable you will feel underwater and the less air you will need to breathe.

How many dives can I do in one day? A recreational dive table can assist divers in answering this question, which many consider to be one of their most difficult. Each recreational dive table displays a time limit for each depth and how long you can stay at it. For example, if you’re diving at 100 feet and the table says you can stay for 20 minutes, that’s the maximum time you can stay. A table indicates that you can stay for up to 20 minutes at a deeper dive, but that is still the maximum time you can spend at that depth. As long as you don’t stay for more than 20 minutes at a time at the deepest dive, the maximum number of dives you can do in one day is unlimited. When diving to a deeper level, the time limit is extended, but the maximum amount of time you can spend at that depth is limited.

## How Far Can You Dive Without Getting The Bends?

Credit: bestscubapro.com

How deep can you dive without Decompression? Divers have no limit to the depth of their dives to 130 feet. It appears that you can go deeper than that and stay within the no-stop limits, but the no-stop times are so short that they are almost impossible to break.

How deep can I dive without stopping my breathing? The depth of the dive and how much time it takes to dive at a given depth determine how frequently compression stops are required. Decompression is more likely to occur when your dive is deeper and longer. Now is the best time to book a scuba diving liveaboard. Diverae slowly as they descend from a scuba diving enclosure. The gases (particularly nitrogen) that dissolved into your bodily tissues under high pressure as you ascended are released as the water pressure decreases. If you accelerate too quickly (e.g. nitrogen), you will cause the gasses to escape and form bubbles.

Decompression sickness (DCS) is caused by nitrogen bubbles in the air. The goal of any dive is to compress the data. A decompression stop occurs when you make a stop on your ascent. The two work in the same way, but if you miss one, you risk developing decompression sickness. Your decompression time will be affected by the depth of your dive as well as how long you stay at the depth. A safety stop is a point of departure on your dive journey that you use as a precaution. A safety stop is not required if you are diving at a depth of between 6-10 metres (20-30 feet).

If you want to dive more than 10-15 meters (30-50 feet) deep, I always recommend having a 5-6 m safety stop. In the comments, tell us about your diving and snorkeling experiences. Please include any other photos you have taken. You can use an underwater camera or a waterproof Gopro camera to capture videos or photos underwater. More Reading is Available: What are the advantages of Nitrox? Russell Bowyer has been a scuba diver for over twenty-five years.

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Before diving into a body of water, you should be familiar with a few things. A maximum of 60 minutes can be spent underwater for the first time. The deeper you go, the longer it will take. Finally, there is a limit to the depth at which you can dive.
If you plan to dive, you should sketch out your dive plan as soon as you get ready. When you are submerged, these are the things you will do and how long it will take you to do them. The plan would be to dive 20 meters (66 feet) for 30 minutes before coming up for a break.
It’s critical to understand your dive schedule in order to make it a safe experience. It is critical that all of your diving partners know their dive schedules so that everyone can follow them. Before diving, it is critical to understand the local regulations.

### How Deep Can You Dive Without Decompression Stops?

Safety stops should be considered standard procedure for all dives that fall below 33 feet (10 meters) due to their ability to reduce the risk of decompression sickness (DCS). The term “safety stop” is commonly associated with a depth of 15-20 feet (5-6 m).

#### Divers Can Stay Submerged For Long Periods At 100 Feet, But Body Is Subject To Great Pressure.

At depths of 100 feet, the body is subjected to greater force than at any other depth. The nitrogen in the air reacts with the nitrogen in the body to form nitrides. Nitriding is much more difficult than nitrogen gas, and without compression, it can cause serious damage to the body.
Decompression is scheduled for dives of 100 feet or more in the United States Navy. Divers can stay underwater for three hours and 45 minutes without requiring decompression at this depth. As a result, the diver may spend almost 5 hours submerged at 100 feet before having to come up for air.

### How Do Divers Not Get The Bends?

Ascending at a speed of 30 feet per minute is not permitted. Make certain that you stop for at least three to five minutes when working at a 15 foot height. The most critical distance for ascending from the safety stop to the boat is the length of time it takes, so slow your pace. Warm up before and during dives.

#### The Bends: What You Need To Know

Divers have long known that diving deeper than 10 metres (30 feet) causes the gases in their tissues to become unbalanced, and can cause bends. However, how deep are the bends?
It is located at a depth of 10 meters (30 feet). bends can occur at depths ranging from 10 to 30 meters below sea level. The deeper you dive, the more bends on your body you will experience.
Will you make it to the top of the world without breaking a leg or a finger if you survive the bends?
People with bends may not have a favorable prognosis or outlook based on the factors listed below.
It is expected that the patient will have good progess after treatment with Hyperbaric Oxygen Therapy. Delay in definitive treatment of Hyperbaric oxygen poisoning: Although divers can recover quickly after symptoms, delaying definitive treatment may result in irreversible damage.
Even if definitive treatment fails to resolve the problem, there is no guarantee that the bends will go away. With treatment, the majority of people have a complete and complete recovery.

## Can A Human Dive 500 Feet?

There is no definitive answer to this question as it depends on a number of factors, including the person’s experience, abilities, and comfort level. Generally speaking, however, most people would not be able to dive 500 feet without some sort of specialized equipment or training. Additionally, the deeper you dive, the greater the risk of decompression sickness, which can be fatal.

You must know how deep you can dive in the ocean without putting yourself in danger if you want to succeed as a scuba diver. Divers can dive up to 1000 feet (around 300 meters) with the right gear and practice. Deep diving begins at 18 meters (roughly 60 feet) and lasts about 18 meters (roughly 60 feet). Deep diving necessitates a slow ascent that includes stops after deep diving to avoid decompression sickness. Deep diving places a lot of strain on the body of a scuba diver. Nitrogen narcosis begins to spread around 100 feet away. If you begin to feel sleepy during your dive, your ascent should begin.

You will be able to get rid of the laxative effect after this procedure and return to the surface to normal. Divers can reach depths of up to 1000 feet with the right scuba equipment. When a diver crosses a certain depth, we can’t tell whether or not he or she will be crushed. The most important thing to pay attention to is that the water is being crushed due to its increased weight. A scuba tank typically contains 21% oxygen and 74% nitrogen in its compressed air mix. Nitrox mixes contain 22%-40 oxygen, with the majority of them containing 32-36%. Divers can enter deeper water without feeling fatigued because helium is an inert gas that does not react with the body.

Divers can use the mix to complete a dive up to 300 meters (984 feet) in height. If you want to deepen the tank, the helium in it must be replaced with hydrogen. As a result, the pressure will squeeze your lungs and slow down your heart rate. You will feel sleepy and spaced out even after consuming it because it has a narcotic effect. Decompression stops as soon as the body’s natural ability to absorb gas dies. Saturation divers breathe with a perfluorocarbon liquid mix, preventing gases from entering their bodies. Scientists have been exploring the depths of the ocean for decades, and it is possible that humans can reach depths of up to 3,000 feet.

Recreational divers are unlikely to come into contact with situations in which a hypoxic trimix cylinder is required. The trimix cylinder, on the other hand, is an excellent tool for exploring deeper water. The trimix cylinder allows divers to go up to 328 feet without being exposed to oxygen toxicity.

Source https://thedivingblog.com/visibility-scuba-diving/

Source https://www.desertdivers.com/diving-in-shallow-water/