Into the Deep Dark Blue: Exploring the Sea with Dive Lights


It is 2015 and, still, a staggering 90-95% of the Earth’s oceans remain unexplored. This seems unbelievable, given the incredible advancements we’ve seen in technology over the years, and the fact that we’ve even explored the Moon and planets in some detail. Indeed, it has been said that we know more about the surface of the Moon or Mars than about the ocean floor. How is it that the vast majority of the ocean, which makes up 70% of our own planet, is as yet undiscovered? It speaks to the sheer vastness and depth of the underwater realm. It also presents an amazing opportunity for anyone who yearns to know the unknown, and to find what has never been found—and in so doing, to make history. Dive lights are one of the most critical tools of the trade for such explorers and adventurers, illuminating everything under the surface and bringing out its beautiful natural colors. In this article, we’ll examine some of these lights in depth, covering their features, capabilities, operation, and applications.

" has been said that we know more about the surface of the Moon or Mars than about the ocean floor."

Seeing the True Colors

Oceans and lakes act as big blue and green filters. At depths of about 15-30', the water starts to absorb colors, turning them into muted shades of blue and green. To see underwater environments and life forms in true, rich, vibrant color, you need a light. Color temperature measures how warm (red) or cold (blue) a light appears, and is expressed in degrees Kelvin, or K. Lower numbers are closer to the warm red end, while higher values are closer to the cold blue end. Virtually all LED dive lights fall into the 5000-7000K temperature range, which is the white to bluish-white portion of the spectrum and is approximately the same color as daylight—often referred to as “daylight balanced.” There are some dive lights, such as the Tec 40 Dive Light from Princeton Tec, that use halogen or xenon incandescent lamps instead of LEDs. These lamps offer a warmer, yellowish light at about 3200K, which some divers prefer because of the more natural color rendering they often provide, but these lamps have higher power consumption, shorter lifetimes and, typically, less brightness than LEDs, so they are not as popular. Additionally, LEDs have seen great improvements in recent years in their color-rendering ability, and are continuing to get better.

Looking on the Bright Side of Life

The light source in a dive light is often a combination of multiple LEDs or lamps for greater power output, and therefore, greater brightness. Most lights use LEDs, which have outstanding lifespans of up to 50,000 hours—good news if you plan on spending lots of time beneath the waves. Dive lights can differ enormously in their brightness, anywhere from 28 lumens in the Tec 40 Dive Light from Princeton Tec to more than 20,000 in the powerhouse Orcalight SeaWolf 1560 and 2260 LEDs. Many fall into the 500-1500 lumen range, which is sufficient for a lot of diving expeditions. If you're doing a considerable amount of exploring inside the underwater caves of Belize’s Great Blue Hole or the popular SS Yongala and Thistlegorm shipwrecks in Queensland, Australia, and the Red Sea in Egypt, you'll likely want something much brighter.

Keep in mind that the farther down you go, to a point, the darker your environment becomes. If you're not much more than sixty feet down and it's a bright, clear, sunny day, you can get away with using a relatively dim beam. Depending upon where in the world you are—say, Costa Rica in the Caribbean, or somewhere very near the equator—you may be able to get away with no artificial light at all at such depths when the sky is crystal clear. But of course, having a flashlight with you—and a pretty bright one at that—is still essential if you want to be able to venture deeper and explore other locations, or if you’re diving at night. Sooner or later, you’re going to need one, so why not just keep it with you at all times?

While a high level of brightness is often important when diving, you also have to think about the effect this has on the underwater life you're trying to see. Bright light shining directly on fish and other critters is quite harsh and tends to scare them off. A diffuser is a good way to soften the beam and spread it out so it's gentler on your subjects. This tool can also improve your own visibility at times, by reducing reflections, glare, and the backscatter from particles in the water. There are also red and yellow warming filters you can add to the front of your light to reduce the brightness and change the color of the beam. These include the Ikelite Red Filter M27 for Gamma Waterproof Flashlight and the Bigblue External Red Color Filter for AL900WP, AL900XWP, AL1000WP, and AL1000XWP LED Dive Lights. Bigblue also makes another model for its VL1800M, VL2500P, and VTL2500P lights.

Some lights even have different color modes, so you can switch from bright white to warm red or mellow yellow with just the push of a button or the twist of a dial. Creatures of the sea do not notice these colors of light, especially the reds, nearly as much as they notice white. So, by altering the hue of your beam, you'll be able to observe the animals you come across instead of chasing them and struggling to get a good look.

For a backup dive light, 200-300 lumens is the minimum you're going to want. Your backup light can double as an illumination source for small, tight areas, such as the spaces between rocks and the nooks and crannies in caves or wrecks, where little sea creatures are likely to be hiding. It can also be used for close-up looks when you want to see all the detail of interesting organisms, like the more than 300 different types of coral in the reefs of Tubbataha, Palawan, in the Philippines. If you’re documenting your adventure in pictures or videos, this type of light can make a great focusing aid, as well.

What's Your Angle?

Just as different levels of brightness can serve you better in various situations, the same is true of your angle of coverage. Lights come in every variety, from extreme wide-angle beams for illuminating shipwreck exteriors, coral reefs, rock formations, and schools of fish, to super-tight, narrow beams that are ideal for use in small spaces and when examining discovered treasure or trinkets, sea creatures, and plant life up close. A tight, bright spot is also very helpful when navigating murky, low-visibility water. A prime example of the wide type would be the Bigblue AL1000XWP Extra Wide Beam LED Dive Light at 120 degrees, while its sister light, the AL1000NP, and Ikelite’s Gamma both represent the narrow type very well at 10 degrees.

While some lights offer one constant beam angle, many models like the Nocturnal Lights TLX 800t do allow for variable coverage. This versatility enables you to switch between a concentrated 8- to 20-degree spot (12 in the 800t) for a close-up look at the diverse tropical fish in the Maldives, and a wide beam of 80-120 degrees (90 in the 800t) for a broad look at that cave mouth in Belize, that immense humpback whale in Queensland, or that throng of barracudas in the aptly named Barracuda Point, near Malaysia’s Sipadan Island.

The lights that provide a single lumen output sometimes actually combine two beams in one. They’ll have a wide overall coverage angle with a tight “hot spot,” or brighter, more concentrated circle in the center. If you’re looking for differential light, such as a brighter center subject and softer, dimmer peripheral subjects and background, this could be an asset. It may allow for some dramatic effects, which you might want if you’re taking pictures or recording video of your expedition. However, hot spots often result in glare, backscatter, and lighting that looks too harsh and unbalanced, so a smooth, even beam with no hot spots is preferred in the vast majority of situations. 

Fluorescence and Filters

Presenting a unique opportunity for divers, there are certain types of coral and other organisms that have properties which cause them to emit a brilliant fluorescent glow when stimulated by specific wavelengths of light. They generally respond to the very dark blues at the extreme edge of the visible spectrum and the invisible waves in the ultraviolet spectrum. Certain specialized lights, such as the Keldan Video 4X Blue Fluorescence and 4X UV Fluorescence LED, are designed to match these wavelengths and create this effect. For other lights, there are barrier filters that can be fitted onto the front to change the beam's wavelength to match the appropriate band of the spectrum. Additionally, some lights will have a deep blue or UV mode that can be selected; others, including the UKPro Aqualite eLED Pro Dive Light (20º) and Pro Video Dive Light (100º), have interchangeable heads, such as the UV-395 eLED that can be attached to emit these wavelengths and generate fluorescence. To be able to observe this eye-catching glow in all its unique beauty, you'll need to wear a barrier mask yourself. Bigblue offers a Fluorodive Kit for VL1800M, VL2500P and VTL2500P Lights, as well as one for their CF250 light and another for their CF450, AL1000, and AL1800 lights. These kits set you up with both the barrier filters and the mask.

Mighty but Mini

One of the primary advantages of dive lights is a very compact, lightweight form factor that’s easily portable. They’re designed to be held in your hand or strapped to the back of it using a glove or other mount offering comfort and freedom of movement. Some lights, such as the 4-oz Ikelite Gamma LED, are even small enough to fit in your pocket as a backup illumination source, which is a highly recommended thing to have at all times when diving—especially in deep, dark waters. Life is unpredictable, and you never know when your primary light could be lost or taken out of commission. It could slip out of your hand and, if it’s negatively buoyant, fall down an abyss or into a deep crack where you can't retrieve it. It could be smashed on a rock. Or, the batteries could simply die. Being prepared means having more than one tool for the job, and taking along a small light enables you to  pack light—making it both useful and convenient.

Under Pressure

The compact size of dive lights means there is a small amount of surface area on which the water can exert pressure. The farther you go below the surface, the greater the water pressure becomes. So, small size is one of the main reasons many of these lights are safely submersible to hundreds of feet below the water’s surface, where the pressure levels are powerful enough to crush many objects.

The depth rating of a dive light tells you just how far down you can take it while keeping it operational. This can vary greatly from one light to the next, with some models capable of submersion to just 30' and others, including the Gamma and the Tovatec Compact LED Dive Torch, rated for 400' or more. The top contenders in this arena, like the Keldan Video 4X Blue Fluorescence and 4X UV Fluorescence LEDs, can withstand the pressure at a remarkable 656'. The rest of the pack falls anywhere and everywhere between the extremes of this range. Aside from size, other factors that determine depth rating are material of construction and the strength of the watertight seal. Lights that can go the deepest, including the Gamma and the 4X series, are generally made of aluminum, which is anodized to resist corrosion. Multiple O-ring seals to prevent water ingress are also critical. The body material provides strength and durability to protect against pressure and the harshness of seawater, but it's the O-ring seals that ensure no water leaks into your light and leaves you in the dark more than a hundred feet below the surface.

Having the light with the greatest depth rating ensures that you can dive virtually anywhere you might like, so it opens up a world of possibilities. But the most durable, pressure-resistant model is not necessarily the best, and you likely do not even have the need or desire to venture so far down. Having all that water within reach presents a great opportunity for a diver, but there are plenty of fascinating things to explore at shallower depths, as well.

Getting a Handle on the Mechanics: Run Time, Settings, and Ergonomics

"It's great to get lost in an adventure, but don’t let the mesmerizing fluorescence and other marvels of the sea cause you to lose track of time completely."

It's great to get lost in an adventure, but don’t let the mesmerizing fluorescence and other marvels of the sea cause you to lose track of time completely. You don't want to find yourself with a dead battery in pitch darkness inside an underwater cave. A light’s run time is a crucial thing to know. Lights will often run for about an hour to an hour and a half on full power, two to three hours on medium output, and six or more hours on low. A select few, including Bigblue’s AL1000 series, can go the distance with outstanding 20-hour maximum run times. It all depends on the capacity of the battery inside and the output level of the light.

Most lights have at least two power settings, high and low, though there are some with a single output and still others with as many as four. Additionally, many lights come equipped with an emergency SOS strobe mode, which will trigger the beam to flash in order to signal for help.

The switching mechanism on a dive light can be a simple push-button, sliding switch, rotary dial, or twisting bezel. Push-buttons are located on the head, body, or tail cap, while a dial is usually positioned where the head and body meet and a bezel is situated on the front of the light, around the emitter window.

A simple push-button switching mechanism  A flat rotary dial A twisting bezel located around the head

Apart from the location and type of switching system, another important factor that determines handling and usability is ergonomics. Ikelite’s Gamma light offers a contoured slip-resistant grip that is comfortable in your hand and provides security against drops. It is narrower in the center than at the ends, which is an unusual design that makes it more difficult for the light to slip out of your hand. Other lights demonstrate a different approach, featuring a more typical cylindrical shape but with grooves or knurling to help safeguard against slipping. Keep in mind that often when diving, especially at deeper depths, you’ll want to be wearing gloves to protect against the cold. This can make it easier or harder to hold your light, depending on the type of glove and design of the light. Going with a “grippy” type with non-slip palms would certainly help, especially when used in conjunction with a contoured or grooved dive light.

Beacons of Hope

Flashlights are, of course, your primary and secondary sources of illumination. But let's say you get unlucky and both your lights are dead, or you got shocked by an electric eel or scared half to death by a shark and dropped them, and now those lights are Poseidon-knows-where. How will your diving buddy—another highly recommended thing to have—find you? That's where wearable lights like the I-Torch i-Buddy Firefly LED Dive Beacon, Bigblue Easy Clip LED Marker Light, and Princeton Tec Meridian LED Strobe come in handy. They shine in various colors to help you identify your friends and vice-versa. If you have multiple teams, buddy pairs are readily recognized by their common beacon colors. Some of these lights are visible from up to a mile away. A select few lights, such as the Pelican Nemo StealthLite 2410 LED Photoluminescent model, have an attached ring, or shroud, that emits a bright glow in the dark for better visibility—giving you a dive light and safety beacon all in one.


The world is full of beautiful and captivating underwater life and natural wonders. Dive lights let you see it all in true, vibrant color. Don't leave the boat without one—two, in fact. Armed with your primary and backup lamps, you'll be prepared to experience the majestic underwater realm and maybe even make a discovery no one else has ever made. The sea is calling, demanding to be explored. Got a light?