Being able to see while underwater is incredibly important for anyone participating in watersports. It can be frightening to head into water only to realize that you cannot even see your hand in front of your face. While water can look clear and safe on the surface, many factors can affect underwater visibility.
Wind and currents reduce underwater visibility by creating turbulence that chops up the surface, reducing the light penetrating the water. Also, currents can stir sand and silt within the water, resulting in a blurry mix. Sudden storms can do this very quickly, affecting safety.
There’s more to water visibility than meets the eye. If you plan on being in or around water for extended periods, you must understand underwater visibility and the factors that can affect it. In this article, you’ll learn the different ways that wind, current, weather, and more elements can affect underwater visibility.
How Do Wind, Current, and Weather Affect Underwater Visibility
Understanding the main factors that affect underwater visibility helps you determine the best time and place to go snorkeling or scuba diving and other water sports that depend on it.
When the wind blows across the water, it causes waves – namely ripples, chop, swells, and breaking waves:
- Ripples: Tiny waves that “ripple” over the water’s surface.
- Chop: Numerous small waves that roughen up the waters.
- Swells: Long, smooth waves traveling far from their source.
- Breaking waves: Waves that reach the coastline, lowering their wavelength and increasing their height.
- Spilling waves break slowly.
- Plunging waves break rapidly.
- Surging waves break in surges.
- Collapsing waves quickly break in surges.
These waves roughen water and also increase light reflection. This subsequently reduces light penetration, leading to worse water visibility the deeper you go.
On a windy day, water loses stillness. Apart from the waves, wind can churn up the sand from the shore and, if strong enough, sediments on the shallow parts of the water body as well. Once the water starts accumulating sand and silt, it becomes blurry and impedes your vision. (Sources: Dive Training Mag and SECOORA)
Water currents (ScienceDirect) are caused by intricate forces related to the sun. They are cohesive streams of water circulating throughout a water body.
Since currents stir up waters in massive scales, they can carry debris for miles. So, if you lost something like your sunglasses in the ocean, you might never find them again in that area. The power of currents makes it easy for them to stir sediments, sand, and other debris hence reducing underwater visibility. They erode the beach and restore the sand after some time.
There are two main types of currents:
|Current||Characteristics||Effect on Water Visibility|
|Surface currents||They form on the surface of a water bodyProvoked by changes in air temperature which causes windTransfers warm, less dense water from the equator to the poles||Carries sand and debris from the coastline which mixes with water and reduces water clarity. Roughens the surface of the water hence reducing light penetration to the deeper sections|
|Deep-sea currents||Occurs in the deeper parts of a water bodyDriven by changes in the density of the waterCarries cold, dense water from the poles to the equator||Stirs up bottom silt which mixes with deep waters|
(Sources: National Oceanic and Atmospheric Administration and U.S Navy Diving Manual)
When you wake up, you might look outside your window or listen to weather forecasting news to determine how the weather is going to unfold during the rest of your day. This is especially vital when you’re planning to explore the waters.
Windy, Stormy Weather
In this kind of weather, sand and debris stir and mix up with water. Moreover, the stormy atmosphere will result in decreased sunshine and subsequently reduced underwater visibility. Even a short storm can cause turbulence, which stirs sand and debris that takes hours and even a day to clear out.
A Rainy Day
Rain reduces the overhead sunlight reaching the depths of water. Moreover, the incoming streams of water might stir up the surrounding sand and debris, blurring objects in your line of sight. Though light rain may not seriously affect your snorkeling (as I discuss in that post) or scuba diving.
Clouds dull the brightness of sunlight. On an extremely cloudy day, the light reaching the waters reduces and affects underwater visibility. The waters might be still, but since there’s no light reflecting off the objects in the water, you won’t see them. Colors become flat, and distances are reduced considerably.
(Sources: Dive Training Magazine, Dive Viz)
Hail and Snow
Like rain, snow and hail affect underwater visibility. The frozen water particles in the air reduce the light penetrating the waters through reflection and scattering of the light while mid-air.
Also, when snow or hail hit the shores, sand and silt might be lifted and washed into the sea. This will have the same cloudy water effect as that of rain and affect underwater visibility in yet another way. However, you can avoid this by going deeper off the shores.
You can read more on this in my post Does Weather Affect Snorkeling?
Other Factors That Affect Underwater Visibility
Wind, current, and weather aren’t the only elements that affect water visibility. Some other factors may be to blame when you can’t see your scuba diving friends anymore.
These are your fellow divers who kick the bottom and provoke the settled silt, releasing a cloudy form that can affect the visibility of water. Commonly, these people lack buoyancy skills and therefore can’t avoid making contact with the bottom. This type of diver is why I prefer very small boats with only a handful of divers. Especially well-trained ones used to navigating tight spots without stirring up the bottom or damaging coral.
If you or your friend is a silt miner, you’ll need buoyancy training until you become a pro. Furthermore, you can reduce the number of people diving in a particular spot to reduce overcrowding that may otherwise cause disorientation and subsequent kicking of silt. By learning how to not stir up the water, you also learn how to avoid damaging the coral.
This kind of water visibility problem mostly occurs during the summer when there’s a lot of sunlight. Algae blooms are caused by a high level of nutrients and ample sunlight entering the water. However, this is more likely to happen when the water is moving slowly.
During algae blooms, the water becomes cloudy, especially near the surface. However, since the algae cloud reduces the light penetrating the water, the underwater becomes darker than usual. This happens occasionally but can last for weeks before it clears out.
As global warming takes its toll, algae bloom increases in many water bodies around the world. Be cautious since some of these algae produce toxins. (Source: Rows & Reef)
Even though there’s no rain around the waters you’re exploring, the water can get murky due to the runoff from the nearby areas where rain or snow melts have happened intensely. Runoff brings sand, silt, and debris to the waters, reducing water clarity in the process.
However, you can avoid this by exploring areas where runoff is rare. This means you’ll have to avoid river mouths. Moreover, you can get away from the shoreline as much as possible as long as it’s safe. The further you go, the clearer it becomes.
Tides are caused by gravitational forces from the sun and moon. They fill and drain large water bodies at different times of day in various parts of the world. As the tide comes in, water levels rise, and as it goes out, water levels lower.
During an incoming tide, water hits the shores in surges and mixes with sand and debris. When the water starts draining, the water goes away, carrying sand and debris with it. Moreover, the surges in water movements roughen the waters and reduce light penetration to the deep ends.
Both incoming and outgoing tides negatively affect underwater visibility when they’re strong. However, when they reduce in strength, the water starts clearing out, and visibility improves. (Source: NOAA)
Underwater visibility is affected when the light entering the water is altered and also when the sand and debris on the areas surrounding the water are provoked. While most are to be blamed on natural occurrences, people can also reduce water clarity. Ensure you assess water visibility before you explore any water and be observant of any significant changes.