Light and Underwater Lighting

Underwater lighting is never just a simple matter of lighting up a body of water; light undergoes a series of changes in the process of illuminating a body of water. The optical properties of the water, the impurities in the water will affect the final lighting effect as the light passes through.

Optical Properties of Water


When light travels from the air to a body of water, the water’s surface reflects some of the light. If the water surface is not calm, it produces diffuse reflections and the image is not clear. If the water surface is calm, this results in a specular reflection and a clear image.

diffuse reflections and specular


Light travels at different speeds through different media. When light passes from one medium to another, its direction of propagation changes, a phenomenon called refraction. Refraction is very common when light passes through different materials such as air, water or glass.

If you put a spoon into a glass of water, you will notice that the part of the spoon that is under water appears to be broken off, which is caused by the refraction of light. As light passes from the water into the air, it changes direction due to refraction.

This causes the object in the water to appear higher than its actual position when viewed from above the water.

Refraction of light


When light travels in water, it is scattered by water molecules, so the light is scattered in the water. This scattering causes the light in the water to have an even brightness, making the water appear to glow.

In addition, the refraction of light will also cause some scattering. Particles and suspended matter in the water can cause light to randomly change direction as it travels through the water, thus affecting the scattering effect. As light is scattered in water, its intensity gradually decreases. This is why underwater scenes look blurry and lose detail in the distance.

Underwater photography

When we take photographs underwater, we notice that the colours and sharpness of the underwater photographs are different from those taken above water. This is because light travels through water and is scattered and absorbed by the water. These phenomena can affect the results of underwater photography.

Photographers often use special underwater photography techniques and equipment to compensate for these effects.

Light Attenuation

As the depth of the water increases, the intensity of the light gradually decreases. This is due to the absorption and scattering of light by water. In shallow water, light can travel a certain distance, but in deeper water the intensity of the light drops dramatically, resulting in poor visibility.

Light is absorbed by water

In lighting areas such as swimming pools, where the water is shallow and generally no more than two metres deep, the attenuation of light is not as pronounced.


Water has different absorption properties for different wavelengths of light. Water absorbs red and yellow light more because they have longer wavelengths and therefore disappear faster under water. Blue and green light have shorter wavelengths and can travel further through water.

The Influence of the Optical Properties of the Water on the Lighting Effect

Interference From External Underwater Light Sources

Part of the light from an above-water light source is reflected from the water surface and the rest is emitted into the water.

If the reflected light from the water surface is too strong, it can seriously interfere with the underwater lighting effect and even cause glare. Some of the light entering the water is absorbed by the water and some is scattered by substances suspended in the water. Therefore, above-water light sources can affect the effect of underwater lighting to some extent.

In this image you can see that the light creates a specular reflection on the water surface and affects the lighting of the pool.

Underwater Scenes Appear Blurred

The diffusing and attenuating effect of water on light can cause underwater scenes to appear slightly blurred. The blurriness increases as the depth of the water increases.

Suspended matter in the water affects the light effect

As you can see, the amount of floating debris in this landscape pond greatly affects the propagation of light underwater. Even with the illumination of the light, it is still blurred underwater.

Looks Shallower Than it Really is

The phenomenon of refraction in water makes objects underwater appear higher than they really are. We often find that the depth of the pool is deeper than our eyes saw before we entered the water. When swimming in a deep pool, it is important to be aware that visual illusions maby can lead to accidents.

Beauty hides danger.

Shading Effect

Suspended objects, vegetation and other objects in the water can obscure and block the transmission of light. This causes underwater scenes to be shadowed and objects away from the light source to appear darker.

Colour Distortion

Due to the light absorption properties of water, the colours of underwater lighting can be slightly off. However, in most pools the water features are shallow and the changes are difficult to see. So this is not something we need to worry about too much.

Decrease in Brightness

The intensity of light diminishes as it travels further through the water. This phenomenon is exacerbated by suspended impurities in the water.

Most current underwater lights have a fixed beam angle and the light they emit is fan-shaped and spreads outwards. The wider the beam angle, the greater the range of illumination and the faster the decrease in brightness with increasing distance.

 LED pool light beam angle
Below are the beam angles of some common LED underwater lights.

When illuminating deeper or more distant bodies of water, high wattage or higher lumens are required to provide sufficient illumination.


In summary, above-water light sources and various factors that affect the propagation of light underwater, such as refraction, absorption, scattering and attenuation can disturb the effects of underwater lighting. However, these effects are not always detrimental. In fact, some lighting designers can use them to create stunning lighting effects.

WAKING Lighting is a professional manufacturer of underwater lighting equipment and we are also experts in the field of underwater lighting knowledge. We have a wide range of products to meet the lighting needs of swimming pools, water features, fountains, hot spring pools, hot tubs, spas and Jacuzzis. If you need to order underwater lighting equipment or have any questions, please do not hesitate to contact us.

Are you looking for a professional underwater light supplier? Contact us now!

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