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Light is not optional in technical diving — it is a primary tool. Whether you are penetrating a wreck, following a guideline through a cave system, or managing a decompression stop in low visibility, your dive light is what connects you to your environment. Redundancy, burn time, and beam quality are not marketing terms here. They are operational requirements.
The Role of Light in Technical Diving
In recreational diving, a torch is useful. In technical diving, it is essential. Overhead environments — caves, wrecks, mines — have zero ambient light. Even on open-water decompression dives, a reliable light allows the diver to read gauges, check equipment, communicate with the team, and monitor the surrounding environment during long stops at shallow depth.
Technical divers do not carry just one light. The standard approach is a primary light plus at least two backup lights. In cave diving, this is a strict rule. The reason is simple: if your only light source fails underground, you are navigating in total darkness — and that is a life-threatening situation. Redundancy in lighting follows the same logic as redundant gas supply.
Types of Dive Lights
Primary lights are the diver’s main source of illumination. Traditionally, these were canister lights — a light head connected by a cable to a separate battery canister mounted on the harness or tank. The canister houses a large battery, providing high lumen output and extended burn times, often 3–8 hours depending on the power setting. Canister lights remain the preferred choice for exploration diving and extended overhead penetrations where maximum burn time is non-negotiable.
Advances in LED efficiency and lithium-ion battery technology have changed the landscape significantly. Modern handheld lights now deliver output levels that match or exceed previous-generation canister lights. Many technical divers — including penetration divers — now use three handheld lights, each capable of serving as a primary. This approach is lower in cost, offers better redundancy, and simplifies the configuration. For extreme environments demanding maximum burn time at maximum output, canister lights still hold the edge.
Backup lights are compact, handheld, and designed to get you out safely if the primary fails. They are clipped to the harness — typically bolt-snapped to chest D-rings — where they are immediately accessible. Modern backup lights commonly deliver 600 lumens or more with burn times of 60–90 minutes on a single rechargeable battery. They should be simple to deploy and activate with one hand, even in gloves.
What to Look for in a Dive Light
- Beam angle — technical diving favours a tight, focused beam in the range of 6–12 degrees for primary lights. A narrow beam cuts through particulate, reaches further, and provides a defined point of reference for navigation and communication. Video and wide-angle work require a broader beam, but that is a different tool for a different purpose.
- Lumen output — more lumens is not automatically better. What matters is usable output — how much light actually reaches the target at distance. A focused 2,000-lumen beam often outperforms a diffuse 5,000-lumen flood in real diving conditions. Consider the environment you dive in most.
- Burn time — your light must outlast your dive with a comfortable margin. For primary lights, plan for at least 1.5 times your expected dive time. For backup lights, the requirement is enough burn time to safely exit the overhead environment or complete decompression.
- Battery type — rechargeable lithium-ion batteries (18650, 21700) are now standard. They offer high energy density, consistent output, and are more cost-effective over time than disposable batteries. Ensure the charging system is reliable and carry spare batteries on multi-day trips.
- Construction — anodised aluminium bodies are the standard for durability and corrosion resistance. Multiple O-ring seals at the head, body, and tail protect the electronics. Depth ratings should meet or exceed your diving depth — most quality technical diving lights are rated to 100–150 metres.
- Switch design — the switch must be operable with one hand, in gloves, in the dark. Twist, push, and magnetic switches each have trade-offs. The switch should also have a lockout function to prevent accidental activation during transport or storage.
Maintenance and Care
After every dive, rinse the light thoroughly with fresh water. Pay attention to the switch area and the threads where the head meets the body — salt crystals accumulate here and can compromise the O-ring seal over time.
O-rings are the first line of defence against flooding. Inspect them regularly for nicks, cracks, or debris. Remove, clean, and lightly grease O-rings with silicone lubricant according to the manufacturer’s schedule. A single grain of sand on an O-ring can cause a flood that destroys the electronics.
Rechargeable batteries should not be stored fully charged or fully depleted for extended periods — both reduce their lifespan. Store them at approximately 50–70% charge in a cool, dry place. Check battery condition before each dive trip and replace cells that show signs of reduced capacity or physical damage.
Before every dive, test the light on all output modes and verify the switch locks out properly. Check the beam for flickering or colour shifts, which can indicate a failing LED driver or a loose connection.
Frequently Asked Questions
Do I need a canister light for technical diving?
Not necessarily. Modern handheld lights have closed the gap significantly — many technical and cave divers now use three handheld lights instead of a canister plus two backups. Handhelds offer better redundancy and simpler configuration. However, for extended exploration dives where maximum burn time is critical, canister lights still provide the longest runtime at high output levels.
How many lights should a technical diver carry?
The minimum standard is one primary and two backups — three independent light sources in total. In cave diving, this is a firm rule. For open-water technical dives, at least one primary and one backup is expected. The goal is that a single light failure never ends or endangers a dive.
What beam angle is best for technical diving?
A focused beam between 6 and 12 degrees is standard for primary lights in technical diving. This range provides good penetration through water, a well-defined reference point for navigation and communication, and sufficient reach in overhead environments. Wider beams are used for video work but are not ideal as primary dive lights.
How long should a dive light battery last?
Your primary light should have enough burn time to cover at least 1.5 times your planned dive duration. Backup lights need enough capacity to safely exit the overhead environment or complete decompression obligations. In practice, modern handheld primaries offer 60–120 minutes on high, while canister lights typically run 3–8 hours depending on the output setting.
How do I prevent my dive light from flooding?
Maintain the O-rings. Inspect them before every dive for nicks, debris, or deformation. Clean the sealing surfaces and apply a thin layer of silicone grease as recommended by the manufacturer. Never force-tighten the head — it should close smoothly. Store the light with the head slightly loosened to relieve pressure on the O-ring during long-term storage.