Light is a form of energy that travels at a rate of roughly 186,000 miles per second. Perplexingly, light travels as both a wave and a particle, changing color as its wavelength changes.
Under the right circumstances, light can penetrate around 3,280 feet into the water, although the circumstances are rarely perfect.
The Science Behind Light and How It Travels
Light travels in the electromagnetic spectrum at constant speeds. It always travels in a straight line unless reflected or altered by an object. Therefore, we only consider electromagnetic wavelengths in the range visible to humans as “light.”
Light sources are either incandescent or luminescent. Incandescent sources emit light through an excess of energy. The sun, for example, is an incandescent source because it’s so hot that light radiates from it constantly.
Luminescent light sources like phone screens emit light in a process of cold-body radiation. These processes involve electrical energy, subatomic motions, and chemical reactions. In any case, the light that comes from a source will travel at the same speed and with the same trajectory.
That trajectory is always perfectly straight. Light always runs straight, and it always moves at, well, the speed of light.
The Difference Between Shorter and Longer Wavelengths
To truly understand light, we need to appreciate that it exists as two things: particles and waves. Wavelengths are the way that electromagnetic radiation extends itself throughout space. Photons are particles that serve as microscopic units of energy.
If you were to freeze light in its tracks, you’d see the photon. If you were to start speeding the light up gradually, you’d see those photons snap into an oscillating wave that wiggled faster and faster as you brought it up to speed. We consider wavelengths within the visible range to be “light.”
When wavelengths shift outside of the range visible to humans, we call them infrared rays, x rays, gamma rays, and so on.
Wavelengths differ in amplitude and frequency depending on the amount of energy that runs through them. We determine the wavelength by measuring the distance between its cycle’s crest and trough (top and bottom).
How Light Creates Color
The spectrum of visible light is only that which is seeable with a human eye. As wavelengths vary within that spectrum, we perceive them as different colors.
That range exists from wavelengths of roughly 400 nanometers to wavelengths of 700 nanometers. Nanometers are very small. One nanometer is equal to 0.000001 millimeters.
It’s nearly impossible to imagine how small that is. The only things to reference in terms of nanometers are microscopic bacteria, subatomic particles, and other tiny things that don’t come into our day-to-day thoughts.
| Color | Wavelength Distance (Nanometers) |
| Violet | 400 nm |
| Indigo | 425 nm |
| Blue | 470 nm |
| Green | 550 nm |
| Yellow | 600 nm |
| Orange | 630 nm |
| Red | 665 nm |
When light reflects off of different objects, its wavelengths get impacted at different rates. So, literally, everything visible around you reflects light at a different wavelength. Even things that appear to be the same color are probably reflecting slightly different wavelengths.
The human eye can see around 100 shades of color, and the gradations between those shades give us the capacity to see around 1,000,000 specific colors. Naturally, we can’t distinguish each of those gradations, so two things that appear to be “yellow” might actually be 20 or 30 nanometers apart in wavelength.
Interestingly, though, different wavelengths do not travel at different speeds. They only oscillate at different rates while the combination of particle and wave constantly moves at the speed of light.
For example, think about a sunset full of blues, reds, and yellows. You experience the full splash of color right as the sun brushes the horizon.
If different colors moved at different rates, you might get hit with a series of blues, then reds, and the yellows would trickle in shortly after. There would be a lag in our experience of most things. Instead, everything hits us at once because all light moves at the same rate.
This is because light has no mass, so there’s nothing to slow it down.
What Happens to Light As It Penetrates the Water
Light bends when it enters the water at an angle. This process is called refraction. Because water is far denser than air, the light slows down, changing its wavelength.
This process is similar to light moving through a lens or a prism. When traveling through a translucent material, light is impacted in such a way that it refracts different colors in the visible spectrum.
The angle at which the light hits and the conditions of the water determine the wavelength that shines through. That said, under the right conditions, light will move through the water in a very predictable way in terms of its color.
Does Water Absorb the Light Energy?
Water is a “selective filter,” meaning that it filters out particular wavelengths first before moving on to the others. As you get progressively deeper, specific colors will stop appearing.
The difference with deep water is typically enough depth to absorb the light energy altogether. If the water’s not deep, the light will still meet the end of its journey as it reaches the sand, weeds, or whatever lies at the bottom.
Light’s energy is absorbed and transferred into heat. Simply hang a bright lightbulb over a glass of water and measure the temperatures before and after to see this process in real-time.
Knowing how light behaves in water is helpful to anglers out there, as most of the visible spectrum disappears in relatively shallow waters. The lures you use in shallow water might be invisible at greater depths.
Let’s take a look at how light behaves at different depths of water.
| Depth | Colors Eliminated |
| 3 feet | Red |
| 16 feet | Red, Orange |
| 30 feet | Red, Orange, High-Wavelength Yellow |
| 60 feet | Red, Orange, Yellow, Most Greens |
| 100 feet | Full Visible Spectrum |
Water filters out high wavelengths first and moves down the scale as depth increases.
Beyond 100 feet, there’s no light to work with. Fishing in lakes and rivers typically won’t put you in jeopardy of losing visibility to fish, though.
Just keep in mind that the deeper you’re fishing, the lower the wavelength of light you have to work with. As you get deeper, you’ll need to rely more on smell and other factors to try and catch the fish you’re after.
That’s why some deep-sea fish are luminescent and produce their own light source.
Fortunately for whales and other animals that use echolocation, soundwaves behave a lot differently in water.
In fact, sound moves much faster in water than through air and can travel thousands of miles without too much interference.
Fish Vision and Deep Sea Angling
A fish’s vision largely depends on its environment and the necessity for vision. Fish that evolve in the depths don’t have a real need for sight because there’s hardly any light in their environment.
Alternatively, fish that live in shallow water benefit greatly from vision. Intermediate fish, though, tend to have some need for sight and are very attracted to visible food. In most cases, they rely on echolocation or smell to get their meals.
Regardless of the need, most fish have the capacity for sight even though their environment doesn’t have a lot of use for it. That makes flashy, light-up lures a little more intriguing to deep-sea fish.
Angling in the depths might require that you use luminescent bait, considering that there’s no light to reflect off of your run-of-the-mill lures.
Happy Fishing & Tight Lines
