Cave DPV Dive Planning

In this article I am going to make an attempt to tackle the subject of proper dive planning while using a DPV when cave diving. I am writing this article to try and dispel some myths that continue to permeate around the cave diving community, as well as try to make the reader consider things that may not have been covered in previous training. In this article I will give guidance on issues that should be considered in DPV dive planning that may have been overlooked in other formats. I need to be clear on one point: this article is not meant as a replacement for formal DPV Cave Pilot training, but instead it should be viewed as supplemental material to a formal class. To that end, I will not be covering emergency scenarios, such as sharing gas or how to tow a disabled diver. I also realize some individuals may find the tone of this article as blunt, and some may even take offense at the words written within. If you find yourself offended by the discussion below, or you find that the recommendations I suggest are overly onerous, perhaps you need to make a careful self-evaluation and re-think whether DPV cave diving is an activity that you are mature enough to engage in.

I want to start off this discussion by shooting a hole through one of the largest misconceptions about DPV cave diving: to be safe while riding a DPV in a cave, you always need to have twice the amount of gas required to swim out from your furthest point of penetration. The thought process behind this rule is simple – scooters are devices that may become disabled for any of a number of reasons; blades on a prop can break, electronic control systems can fail, o-ring seals can fail, etc. Based on this wrong mindset you need to be prepared to swim out of the cave when (not if) your scooter dies at the maximum point of penetration.

The way that dive planning is presented in this model is that a diver swimming at approximately 50 feet per minute with a surface air consumption rate of approximately 0.75ft3 per minute, will need to keep approximately 250ft3 of gas in reserve for a dive to 2200’ at an average depth of 90’.

Mathematically, this can be shown by knowing some basic formulas which are used to calculate (a) the amount of gas a diver uses in any given minute at depth and (b) the amount of time it will take to swim a given distance. With these two pieces of information, we can then calculate (c) the amount of gas the diver will need to keep in reserve. Please see the appendix below for an explanation of the mathematics.

While this sounds great on paper and is probably suitable for planning a scooter ride to the Hinkle in Devil’s Ear, it is my belief that this method of planning a DPV cave dive is overly simplistic and may lead people to think that their safety is ensured simply by bringing twice the amount of gas they require to swim out. The challenge is that this model breaks down rapidly once the DPV pilot ventures beyond the simple confines of relatively shallow caves and short penetrations.

Let me first explain how this approach fails on a deep dive.

A deep DPV cave dive that many people have done involves scootering upstream Eagle’s Nest to King’s Challenge and The Green Room, a distance of roughly 2200’ from the exit. The dive usually has a round-trip bottom time of less than 30 minutes with a total run-time of around two hours. However, any diver that attempts to swim out from The Green Room will find that with little flow, such a swim will likely take 60 to 70 minutes and during that exit the diver will consume roughly 400ft3 of gas. This means any diver using the “always carry twice the gas to swim” approach should carry 800ft3 of reserve gas for such an exit, a ludicrous amount that can only be met with a full set of double 104’s and 6 stage bottles. Additionally, with an average depth of 240’, such a swim is likely to increase the mandatory decompression obligation incurred by the diver by 4 or 5 hours! Woe is the diver that added 5 hours to their decompression obligation but failed to add several hours-worth of emergency decompression gas.

Because of the absurd amount of reserve gas needed and the increased decompression obligation such a swim would incur, clearly the strategy that to be safe you only need twice your swim out gas will not work on this deep dive.

Now let me shoot a hole through this same approach on a long-range scooter dive in a relatively shallow cave.

Several modern scooters allow a diver to go 8, 9, or 10,000’ into a cave (and out!) with no problems and any person that has the financial means to drop between $5k to $10k can own one. Isn’t technology great?

With an average depth of 85’ and literally miles of trunk passage, Manatee Springs beckons the person who just bought the new Zoom Zoom Extreme model DPV, which is rated by the manufacturer to go 20,000’ of travel distance. Carry enough stage bottles, point the scooter in the right direction, and whoosh you’re heading off two miles away from Catfish Hotel.

Now imagine this scenario, you are 10,000’ back and the electronics package in the Zoom Zoom Extreme scooter dies, rendering it non-functional. Thankfully, Manatee has a lot of flow and it may be possible to exceed a swim speed of 50 feet per minute and potentially even swim as fast as 60 or even 70 feet per minute. While swimming out may sound easy enough, even at the ridiculously fast pace of 70 feet per minute, it will take you close to 2.5 hours to swim out of the cave.

Let me repeat that for emphasis. Assuming you are able to sustain a maximal effort and swim at a pace of 70 feet per minute, it will take you over 2.5 hours to swim out from 10,000’ in Manatee springs.

I want every person that is reading this article to stop for a minute and conduct an honest self-assessment. How many of you can truly say that you have the physical fitness and stamina to sustain a maximal effort swim for 2.5 hours? I didn’t think so.

If you are not regularly engaging in cardio workouts that last more than two-hours at a crack, the likelihood that you will be able to swim out from 10,000’ is NIL. In addition to the physical demands such a swim will place on your body, you will also go through over 400 cubic feet of gas during that swim (a set of 104s plus 5 stage bottles).

Some of you may be thinking “well, we could get a tow from our buddy!” The reality is that towing a buddy over a distance of 10,000’ is going to be challenging in the best of conditions. Add in the complexities of a cave with a large amount of vertical change and many restrictions along the way, and you may quickly realize getting a tow from 10,000’ is not a viable option either.

So how do we make DPV cave diving truly safe?

This may sound a little uncomfortable, but DPV cave dives will always carry an element of risk and they will never be 100% “safe.” However, we can minimize our risks and make DPV cave diving safer by recognizing that swimming out of a cave should never be part of your dive plan and thus we should plan our dives appropriately.

The first element of proper DPV dive planning is knowing the true capabilities of your scooter and not exceeding them. Just as no one in their right mind would consider entering a cave without a working pressure gauge or knowing how much gas is in their tanks, only a fool would begin a long or deep DPV cave dive without knowing how far their scooter can safely travel round-trip.

To know how far your scooter can safely travel, you need two pieces of information: how much energy your scooter uses under maximal work (LOAD) and how much energy your batteries can currently store (CAPACITY). Finding out this information involves conducting some tests on the motor and periodically burn-testing the batteries. I cannot understate this, periodically burn-testing your batteries is very important for safe DPV cave diving. As batteries age, they lose their capacity to store energy and their effectiveness diminishes. A battery that held 1000W of capacity when it left the factory may only be able to hold 860W two years later and you would need to limit your dive plans accordingly.

The prudent DPV pilot that regularly pushes their scooter close to its limits will burn-test their batteries at least once a year.

Armed with the knowledge of how many watts your battery pack can hold and the load your scooter generates, you can get an idea of its real range. A battery pack that holds 860 watts of energy will realistically last for 170 minutes in a DPV that consumes 300Wh under load.

If you know your scooter batteries will only last for 170 minutes, then hopefully you realize that you cannot ride that scooter into a cave for 150 minutes and expect a positive outcome when you turn to exit – you will come up short and kill your battery on your way out. You should never plan a dive that uses all of your battery capacity, planning a dive that kills your battery leaves you with zero safety margin and risks damaging the battery too!

Usually, I try to plan my dives so that I use no more than 70% of my battery life for the entire time I am on the trigger. This leaves me with a little bit of extra capacity in the event I need to tow extra equipment, or for brief periods, a buddy. Planning to use no more than 70% of the capacity also minimizes the risk of harming the battery.

There are several things that may impact how I distribute the time between penetration and exit. Factors I consider include diving in a siphon versus a spring, the amount of flow in the system, and how much additional equipment I will be carrying. Generally speaking, as a starting point you can split the time in half whenever you are diving into a spring. This means that if you have a battery pack that can run for 170 minutes and plan to use 70% of the capacity, you can use the scooter for 60 minutes while going in and 60 minutes while exiting.

That covers staying within the true capabilities of your scooter, but now let me discuss the second thing we can do to make DPV cave diving safer. While hitching a tow from a buddy may be sufficient for a short penetration in a shallow cave, it is not a realistic option for a long or deep cave dive. This means you need to bring spare scooters whenever you either go deep or go long, and only you can decide when spare scooters become a part of the dive plan.

Let me be clear on this point, every individual that is engaged in cave diving has to be a responsible adult that makes their own decisions on where the threshold is when “buddy tow” ceases to become an option and “spare scooter” becomes mandatory. However, I would suggest that any time that you are going deeper than 120’ or further than 3000’, that is when it becomes time to start packing a spare scooter. How many spare scooters a team brings will depend on the complexities of the dive and the capabilities of every member in the team. If you are not regularly practicing towing techniques, you should probably plan on bringing a spare scooter for each diver in the event you have two scooters that wind up becoming disabled.

I know this part stings, because it means that now that you bought your Zoom Zoom Extreme DPV, if you have any intention of using your DPV to the limits of its capabilities you also need to have a second scooter as a backup. The good news is that you do not need to buy two Zoom Zoom Extreme DPV’s, but the bad news is your tow scooter better be reliable because it has to be more than sufficient to get you out from the furthest point of your dive.

In conclusion, DPV cave diving is a lot of fun, but safe DPV cave diving is not as simple as carrying twice the amount of gas as needed to swim out. While swimming a DPV out or catching a tow from a buddy may be an acceptable answer for relatively short distances in shallow caves, that model breaks down rapidly once you start taking your scooter deep or taking it on long cave dives. If your dive plans include deep or long penetrations, you need to consider other options and give up the idea of swimming out.

Appendix: Figuring out the Maths

The purpose of this appendix is to try and help an individual understand the mathematics covered in the above article.

    1. To calculate the amount of gas a diver uses in any given minute at depth, you need to multiple the individual Surface Air Consumption (SAC) rate by the depth, as measure in absolute pressure (ATA). The formula is RMV = SAC * ATA
      In practice, the average experienced technical diver has a swimming SAC rate of 75ft3. If your SAC rate is unknown, you can probably use 0.75ft3 per minute as a starting point.

      The formula for converting the depth of the dive into pressure (ATA) is calculated with the formula ATA = (DEPTH ÷ 33) + 1. If we plug 90’ into our formula, (90 ÷ 33) + 1, we get an ATA of 3.7.

      Therefore our average experienced technical diver has an RMV of 2.8 cubic feet of gas per minute while swimming at a depth of 90’ (0.75 SAC * 3.7 ATA). This means that for every minute the diver is at 90’, he is using 2.8 cubic feet of gas.

    2. To figure out the amount of time it will take to swim a given distance involves knowing a realistic swim speed, as measured in feet per minute. Many things can impact your swim speed, including the amount of drag from the gear that you are carrying, the amount of flow either going with you (exiting a spring) or against you (exiting a siphon), and your stamina and cardiovascular fitness.Generally speaking, most technical divers should be able to sustain a swim speed of up to 50 feet per minute when exiting a high flow spring, but that rate may be reduced to as little as 30 feet (or less!) per minute in a low flow spring, and even less in a siphon.

      The formula for calculating the time it will take to swim a given distance is TIME = DISTANCE ÷ SWIM SPEED.
      A diver exiting a high flow cave, such as Devil’s Ear, from 2200’ of penetration can reasonably expect that swim to last almost 45 minutes (2200 ÷ 50) = 44.

    3. The formula for calculating the amount of gas needed to swim out from any given distance is GAS = RMV * TIME. This means our average technical diver will use approximately 125ft3 of gas to swim 2200’ out from a high flow cave (GAS = 2.8 cubic feet per minute RMV * 44 minutes TIME).Using our “twice the amount of gas needed to swim out” standard, the diver needs to carry 250ft3 of emergency reserve gas to be safe on the cave dive.
    4. Calculating the load that your scooter generates may be a little tricky, as many manufacturers are not forthcoming with that data and there are many things that will impact the load a motor generates, such as drag and speed. However, one “hack” that many people have used is to begin with a fully charged scooter, ride it for 30 minutes on full, then recharge the battery while using a WattsUp meter to measure how many watts went back into the battery while recharging. You can then double that number to get the load in Watt-Hours (Wh).So, if your WattsUp meter records 150 watts when recharging a battery after you had ridden it for 30 minutes at full blast, then your scooter probably generates somewhere close to 300Wh of load on full.
    5. To perform a burn-test on your batteries, take a fully charged scooter and put a WattsUp meter in-line between the battery pack and a resistor pack. The WattsUp meter will display the watts consumed as the resistor pack drains the battery.Two pieces of warning! The first is you need to know what the low voltage cut-off threshold is for your battery pack and be prepared to remove the resistor pack before you hit that threshold, or you risk doing damage to the battery. The second is the resistor pack will get extremely hot while you are doing a burn test, you should conduct the burn test outside and away from flammable materials.

    6. Once you know how many watts your battery pack can hold, you can get an idea of real burn-time by using the formula HOURS = WATTS ÷ LOAD. You can multiple this result by 60 to calculate the number of minutes the scooter should be good for. So, a battery pack that holds 860 watts of energy will realistically last for 170 minutes in a DPV that has a motor that generates 300Wh of load, (860 ÷ 300) * 60 = 172.
    7. I never plan a dive to use more than 70% of the battery capacity. To calculate the dive plan upper limit, I use the formula TIME = REAL_BURN_TIME * 70%. So, if my battery is useful for 170 minutes, I would not plan a dive involving more than 120 minutes on the trigger. 172 * 70% = 120.

Lights are life support!

So you need a primary light?

A question I get asked frequently is “what primary light should I buy for cave diving?” Although light and battery technology is constantly changing, I am going to explain some general guidelines for things to look for in a primary light that will hold true no matter what lights are on the market in the coming years.


Primary Lights Are Life Support Equipment

The first thing I want to address is the basic tenet that lights used in cave diving are life support equipment. Caves have no natural light and cave diving is hard on your gear so you want a light that will provide you with ample lighting and can handle the rigors of cave diving.

This means you should plan on making an investment in a quality dive light from a reputable manufacturer. For a person that is interested in cave and technical diving in North America, I would look at lights made by Dive Rite, Halcyon, Light Monkey and Underwater Light Dude. All four manufacturers have solid products with great customer support and they develop their products with cave diving in mind.

Let me be very frank with you. Primary lights break and eventually it is likely that yours will break too. In 13 years of active cave diving, over a 22-year period, I have yet to own a light that has never failed on me.

Halcyon? Yup, had one fail. Dive Rite? Yup. Light Monkey? Yup them too. And although I’ve never owned an Underwater Light Dude, I know a couple of guys that had failures with theirs too.

In most cases, the failures are wear and tear items – batteries eventually die, light cords and switch boots need periodic replacing, etc. But occasionally the failure may be more dramatic (I blew up an LED emitter once). By having a light that was made by one of the companies listed above, I know that when it breaks, getting it fixed will be quick and easy.

I also know that any light made by one of those four manufacturers will have excellent build quality, fit and finish. It will be well made and should be able to handle a fair amount of wear and tear (i.e. abuse) from cave diving.

Sure, you may save some money up front by buying a cheap foreign made light, but the amount of frustration and aggravation you will encounter due to lost diving opportunities and time spent fiddling with the gadget will more than eat up any savings. And wouldn’t it stink to find out that the company that manufactured your light disappeared overnight and now you can’t get it fixed?

If you go the “cheap route” and buy a no-name foreign light, you will likely wind up buying a top end primary light eventually anyway, so why buy twice?

Price wise, buying a good primary light means you’re probably looking at spending at a minimum $700 and more likely around $1200. I know that is difficult for most of us, but as I said up front, primary lights are life support, how much is your life worth? If you look around, you can probably find a good deal on a used light by one of these manufacturers too – I have a friend that bought an older technology HID light for $350 because he was patient.

Whew, now that that is out of the way, let’s talk about some specifics of what to look for in a light.



I’m a firm believer that you want a light that has a “Goodman” style handle. This means that light head rests on top of your hand, rather than being held in the palm of your hand. The advantage to you is that you will be able to use your fingers to grab and hold things while you are still using the light.

Goodman handles come in either hard or soft types. I personally prefer a hard Goodman handle that is adjustable to the thickness of my hand. The advantage to the hard handle is you can very easily swap back and forth from left to right hand and it rests easily on your hand.

Others prefer the soft handle because, well, it’s soft and they find that more comfortable.

You will need to decide for yourself which you prefer, hard or soft Goodman handle.

Canister or Handheld

When I started cave diving our primary lights had very large lead acid battery packs that were very very very heavy. We had no choice but to have the batteries in a canister and a light head that was connected by a cord.

With the advancements in batteries and LED emitters that we’ve had in the past decade, this is no longer the case and there are some excellent handhelds on the market.

The new Dive Rite H50 can be converted from a traditional canister light to a handheld


Some of the pros to having a handheld light are that you do not have a light cord that is a potential failure point and they’re small enough that you can keep an extra one in a pocket in the event of a light failure.

The trade-off is that the entire light is encapsulated in one package and there is more weight on your hand.

Personally, I am still using a canister style light, but I can see myself picking up a handheld in the not too distant future (are you listening Santa?).

Canister lights have a couple of advantages and disadvantages over handhelds too.

First, and probably most important, is that they can handle much larger battery capacities which means you can get more dive time out of them. However, with most handhelds providing a three to four hour burn-time, this may not be a big consideration for the majority of divers.

The second advantage is that most battery packs can be fitted with an E/O connector. The E/O cord allows you to unplug the head from the canister underwater. A pro to this is that you can swap the head in the event of a failure, but the cons to this are that you may accidentally unplug the light head if the cord gets caught on something (been there, done that) and the E/O connectors can corrode if you regularly take them into salt water. One serious advantage to the E/O connector is that you can also use the battery pack for something else, like a heated undergarment or with a different light head. Once again, this may not be a big advantage for most people, but it is worth noting and these are some of the reasons why I’m not ready to get rid of my canister lights just yet.

A third benefit is that in the event you drop your light head, a corded light will still be attached to you by the cord. Of course, as I said above, if you’re using an E/O connector it is possible for the head to pop off from the battery and to lose the head (yup, I did that one too).

The major con to a canister light is that the light cord is a potential failure point. As I mentioned in the beginning of this article, cave diving is hard on gear. My experience has been that I’m replacing light cords every 18 months, and I have even once nicked one causing a canister flood.


Batteries and Burn Times

Over the years, primary lights have been made with different battery technologies.

A HID light with a Lead Acid Battery Pack (circa 2000) and a LED light with a NiMH battery Pack (circa 2015). Both lights have an approximately 5 hour duration but slightly different size and weight.


NiCAD batteries, both wet and dry cells, were used for many years, but they had various problems including battery memory. These batteries were replaced by Sealed Lead Acid “Gel Cells,” which were the standard throughout the 90s. The SLA batteries were very heavy, but the batteries did not suffer from memory issues and they were very inexpensive to replace, which was good because you had to replace them annually.

Currently, most primary dive lights are made using either NiMH or Li-ion cells. These cells are substantially more expensive than previous technologies, and are a major part of the cost in today’s lights. Both battery technologies have some unique characteristics that you should be aware of.

NiMH – NiMH batteries do not have the energy density of Li-ion batteries. This means you need a larger physical size to store the same amount of energy. NiMH batteries, if charged and then left unattended, will slowly discharge over time. This means you should top up any NiMH battery pack the night before a diving day just to make sure it is fully charged. NiMH batteries can be cycled between 500 and 2000 times, depending on the cell, and a good NiMH battery pack that is well maintained will last for years.

One major downside to a NiMH battery is that it will generate a constant, or near constant, voltage as the battery is used. This means it is very difficult to detect how much of the battery capacity has been used and your light may function “as normal” until it cuts out without warning because it has been drained. Some light manufacturers have developed circuits that can detect the slightest drop in voltage, and will alert you when the battery is getting close to being discharged.

Li-ion – Li-ion cells have much higher energy density. This means a smaller pack may have a longer burn-time. A fully charged Li-ion pack can be left unattended for extended periods without losing a charge. Li-ion packs have a much shorter usable life-span, they typically start losing their ability to hold a full charge after ~300-400 cycles. Li-ion cells also have a more linear drop in voltage as the battery is used, which means that it is easier to detect when a battery has been used and how much of the capacity is remaining.

One con to Li-ion cells is that the FAA has regulations regarding lithium batteries and you need to make sure you understand the regulations and the impact regarding any particular Li-ion battery pack you may have. While your light manufacturer should be able to provide you with a written statement regarding air transportation and the battery pack for your light, there is an upper limit to what you can take on a plane. Note this means you should not pack a Li-ion battery pack in your checked baggage, but instead you must carry them on with you.

Both NiMH and Li-ion batteries do not fare well in hot environments. Leaving them in the trunk of your car on a hot summer day will damage them and shorten their usable life. Li-ion batteries should not be left fully charged for extended periods of time either, that is bad for the cells.

What about SLA (Lead Acid) batteries? I cannot think of a manufacturer that is currently producing a light with lead acid batteries, however, you may run across a used light that has them. The major downside to SLA batteries is their weight for the amount of battery capacity, but if you are willing to live with that in order to get a primary light for a slightly reduced price, they may be a good option for you. SLA batteries are very inexpensive, I recently replaced a set for $30. They also only last about 100-200 cycles, so you will need to replace them on a regular basis.

What about Lithium-Polymer (LiPO) cells? A LiPO battery pack is essentially the same as a Li-ion cell, but with the battery electrolyte in a flexible bag rather than a rigid container. There have been a large number of fires caused by bag rupture or distortion, just think about the recent spate of Samsung phone recalls. I consider LiPO cells unacceptable for diving applications because I personally believe the rigors of cave diving will put the cells at risk of damage, meaning they could potentially spontaneously catch fire – yikes!

No matter what battery technology you wind up with, you want to get a light with at least three hours of burn time. Although you may only be doing 1 hour dives right now, it’s very likely to do two or three 1 hour dives in a day, and you want a light that will last for a full days worth of diving. My general rule of thumb is I want a light that will last for 50% longer than my planned dive day, so if you are planning for 2x one hour dives, you want at least three hours of burn time.

One thing is for certain, you will eventually need to replace the batteries and periodic testing of the health of the batteries will allow you to know when you need to replace that pack. I try to burn test my lights at least once every six months and at the bare minimum I test them annually. There are multiple ways to test a pack, including using specifically designed battery test gear, but I prefer to use a low-tech method that gives me accurate and reliable numbers and did not cost me much to assemble.

My simple test consists of filling a 5 gallon bucket with water, turning on my fully charged light and placing it in the bucket. I then start a stop watch and keep periodic tabs on the light until it dies. For the first 90 minutes I ignore the light, but after that I begin checking it every 20 to 30 minutes to make sure it is still working. Once I get within 30 minutes of the expected burn time, I begin checking it every 5 minutes.

After the burn test is complete, I re-charge the pack and make a note of the burn-time in a log-book that I keep for this purpose. This allows me to compare the health of the battery to the previous burn test, and I can proactively replace the batteries when the burn test gives me 80% of previous tests.

The author burn testing a lead acid battery pack. The bucket of water prevents the light head from getting damaged by overheating.



Lumens versus Lux and Lord Kelvin

Pay close attention to advertising that describes a light by Lumens and advertising that talks about Lux because those advertisements are describing completely different beasts with different numbers (700 lumens, 10,000 lux). Making sense of what those numbers mean would require a PhD in optical physics, or at least it feels that way sometimes, but I’ll try to explain this in an easy to understand way.

In simple terms, “lumens” is a measure of the total amount of light output, and “lux” is a measure of how much of that light output hits a fixed target at a set distance away. Comparing lumens numbers is pretty straightforward, but when comparing lux it is important to also make sure you are comparing the distance from the light source. One vendor may advertise their lights with a lux rating based on a 3m (10’) distance and another may advertise it with a 1m (3’) distance and those numbers would be drastically different.

Although higher output numbers seem like they should correspond to a “brighter” light, this is not necessarily the case for a couple of reasons:

  • Light output is determined by the total amount of light coming out of the front of the light.
  • Peak beam intensity represents brightness as perceived by the human eye, and it is related to how the beam is focused by the entire system, including the reflector, lens, or optic.

So, which is more important? At the end of the day, what you will likely care about is how much light gets emitted and I tend to believe that when you start going beyond ~700 lumens, the more interesting thing to look at is the Kelvin (“temperature”) of the light. The higher the Kelvin, the whiter the light and once you go above 6000K, the color in the cave will really begin to “pop.” What I mean by this is that the blue in the water will stand out and colors in clay banks will be rich and natural, basically everything will look better at 6000K.



There are two competing light technologies currently on the market, HID and LED.

The venerable 21w HID was the preferred light of many for several years


HID uses a gas arc system that requires a ballast to function. The advantages of the HID system are that they are very bright, they operate at a high Kelvin temperature, and the beam can be focused from a broad wide angle to a precision “laser” dot. The down-sides to them are that the ballast or bulb can fail, they have a higher power consumption, and it is expensive to replace a bulb if they break.

LED uses an electronic emitter that is solid-state and robust, it should last for well over 5000 hours before failure. Until recently, the main down-side to the LED lights were that it was nearly impossible to focus them and they lacked the “punch” in murkier water that HID offers. The advantages of LED are that they will last a long time and they typically have a lower power consumption.

Although my primary “go-to” light is currently a 21w HID, I believe that modern LED lights are now at a point where there is no longer a reason to purchase a HID light unless you have a very specific reason for one.

What about Halogen/Xenon? Well, filament based bulbs were very popular years ago, and the bulbs are incredibly cheap to replace, but those have gone the way of the yoke manifold and dodo bird and should be retired.



In cave diving, we use our lights as our primary means of communication. We know our teammates are with us when we see their light beam and we use our lights for highlighting an interesting feature, signaling OK or signaling distress. Because we use our lights for as a primary source of communication, I’m a firm believer that any light used for cave diving should be able to have a tight focused beam. We call that tight beam the spot. My recommendation is that a primary light for cave diving should have a beam angle of no greater than 8° and a tighter beam, such as 6°, is preferred.



I started working on this article two months ago, and as I am wrapping it up, two of the manufacturers have just announced new lighting systems which offer brighter lights with multiple battery options for 2017. As I said early on in this article, technology is continually marching forward, but there are a few guiding principles to think about when selecting your next primary light:

  • Lights are life-support. Avoid cheap crap just because it’s inexpensive.
  • Goodman Handle.
  • Battery Technology should be Li-Ion or NiMH with a minimum 3 hour burn time. Burn time is affected by the light head.
  • Batteries should be tested every 6 months.
  • Should have at least than 700 lumens, with a Kelvin temperature greater than 6000.
  • Should have a focused “spot” of no more than 8°; 6° is even better.

Dive safe!