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The DIR-knot


Do you need to attach a clip to a hose, SPG or backup light? Struggling with figuring out how to do it?

Maybe you have been told that there must be no metal-to-metal connections. Maybe you have seen other divers use zip-ties, o-rings or special breakaway contraptions that are single use.

When you attach a piece of equipment to yourself or to your rig there are a few factors to consider. First of all, the attachment must be reliable and dependable, it should not come loose. Second, for safety, in an emergency, it must be possible to disconnect, either by force or with your dive knife or cutting tool. Also, it is an advantage if it is a simple, cheap and readily available method.

Let us take a look at the DIR-knot. You will need a piece of string, approximately 30 to 50 cm, depending on what you want to attach. You will find suitable line on your spool or reel. You will also need a cutting tool (dive knife or similar) and a source of heat, such as a lighter.

Tying the DIR-knot

First, place the two items you want to attach next to each other. Work on a surface where you can position the items so you can use your hands to manipulate the string.

Make sure the string is long enough to grip so you can tighten the knot thoroughly, with some force. Start by threading the string behind and up through the eye of the clip.

Thread through clip.
Thread the string through the eye of the clip.

Three turns

Then continue by looping the line around the two items three times. Try to align the string so that the three turns sit nicely in order, next to each other, from left to right. This will make the knot tidy and look good but also improve its reliability.

Pass around.
Pass the string around and then through the eye of the clip again.
Repeat for second turn.
Repeat the previous steps again for a second turn.
Repeat for third turn.
Then do a third turn.

Overhand knot

Make an overhand knot on the first side. If done right it will sit nice and perpendicular to the three turns. Tighten the knot as much as you can.

Cross ends.
Cross the ends of the string, and…
Make overhand knot.
…make an overhand knot
Tighten overhand knot.
Tighten the overhand knot.

Turn over

Carefully, while keeping the overhand knot tight, turn everything over.

Turn over.
Turn everything over so the overhand knot faces away from you.

Reef knot

We will make a reef knot. A reef, or square, knot is essentially two overhand knots on top of each other. One done left over right and the other right over left (or vice versa).

Make an overhand knot. Just like on the first side. Left end in front of the right. Tighten well.

Cross strings.
Cross the strings, left end in front of the right end, and…
Make overhand knot and tighten.
…make another overhand knot. Tighten.

Try to keep the first overhand knot tight while making another one. This time with the right end in front of the left. The knot should be square and symmetrical. If it is not, it is a granny knot, which will not hold as well.

Cross strings again.
Cross the strings again, this time with the right end before the left end.
Make another overhand knot.
…make another overhand knot over the other.
Make a reef knot.
Forming a reef, or square, knot. Make sure it is symmetrical, a granny knot will not hold as well. Tighten.

Melt and trim

We are almost done. Just need to trim and secure the ends. Start by cutting them. Leave about one centimeter of string on each side.

Cut one end.
Cut one end.
Cut other end.
Cut the other end.

Then carefully, using the lighter, melt each end. Take care so you do not damage any of the attached items. Use the back of the lighter, pressed to the melted string, to flatten the ends and create a mushroom shape. This stops the knot from unraveling.

Melt end.
Use a lighter to burn and melt the end.
Press melted end into mushroom.
Then use the lighter to press the melted end into a mushroom. Repeat for the other end.

Check the knot

You are almost done. Inspect your handiwork. Eye the knot, check that you made a square knot. Pull and twist on the clip to make sure the knot is good. Now you have a secure attachment of one item to another. In an emergency you can cut the items free with a knife or cutting tool.

You are done.
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Buying a primary light

Choosing a dive light

As a new diver, one of the first pieces of equipment to get is a dive light. When shopping for a light there are a few factors to consider.

What type of diving do you do? Are you limiting yourself to daytime, tropical, warm water diving? Will you want to try night diving? Do you dive at home as well as on vacation? Are you an advanced technical diver or a cave diver?

Read more, we have the primary light for you.

The Agir light system

The Agir light lineup is encompasses a broad range of modular products that is suitable for all types of diving.

Our flagship, the 34 Ah 28 W LED with dual outputs is a light for the diver that needs lots of power and illumination during really long dives. The 28 W LED light head outputs approximately 4000 lumens in a tight spot with a pleasing corona. The secondary output can be individually controlled and connected to heated undergarments providing comfort during really cold dives.

At the other end of the lineup we find the convenient 2 W LED Arthur backup light. Small enough to conveniently fit into a BCD pocket, but best mounted with a clip on your shoulder strap. In between these two extremes are one of our most loved lights; the 10.4 Ah 10 W LED canister light.

The 10 W LED with the 10.4 Ah battery pack is used and loved by many divers. It demonstrates a great tradeoff between canister size and weight, light output, burn time and economy.

A modular system

The Agir range of primary lights are modular. An Agir primary light is composed of three main components; the light head, the battery pack and the lid.

Our canisters comes in four different sizes; the largest 34 Ah battery, the big 18.2 Ah battery, the 10.4 Ah battery pack and finally the 3.2 Ah battery pack for the handheld light.

We offer two (three) different light heads, first the big 28 W LED head, then the 10 W LED light head and also the 10 W LED light for the handheld convertible light.

The lids come in two sizes; 70 mm for the 10.4 Ah and 18.2 canisters, and 90 mm for the 34 Ah canister. The lid can be either the standard lid with one output or the dual output variant.

Between the lid and the light head is a cable. The cable is either a continuous cable or it can be a wet-mateable e/o connector cord.

This modular design provide a wide range of variations, in fact, 32 different lights can be put together using our light heads, battery packs and lids.

A light for every diver

The modularity means that, if you are looking for a primary light: we have it.

Modularity has a number of benefits. First of all, it means that we have the best light for you. Among all the different variations, there is a light that is tailor made just for you.

Upgrades are painless

Second, if you ever feel you need to upgrade, maybe from the smaller 10 W LED light head to the bigger 28 W LED light head, you do not have to buy a new primary light. Just get the bigger light head and connect it to your canister. If you would like to be able to swap between the 10 W head and the 28 W head, you can either attach a new lid to the new light head or you could swap the standard cables for e/o connectors on both your heads and on your lid. Each solution has its benefits.

Travelling and diving

For the travelling diver, a great solution is our handheld 10 W LED primary light combined with a cable-to-lid adaptor and a canister style battery pack. Use the smaller handheld battery pack for travel to save weight and space in your luggage. When diving at home, maybe in cold waters, use a big 18.2 Ah canister with dual outputs to power both your light head and your electrical underwear.

Replacing parts

While our lights are robust and hard wearing, sometimes, after many years of service, parts may need to be replaced. Modularity means you do not have to get a new light. Instead, for example, just switch a worn out battery pack for a new, fresh one.

Grows with you

Modularity also means that your light grows with your diving. If you see yourself mainly doing diving during vacations to tropical destinations, then get the 10 W handheld primary light to start with. It is small and light, but provide the same light output as our most successful primary light the 10.4 Ah 10 W LED light.

Whenever you feel like you want to advance your diving career and need a canister style primary light on a Goodman grip: just add an adapter and a canister and put your light head on a Goodman grip. You can now use your light as a handheld torch on vacations and you have an excellent canister light. Later on you may want a dual output lid to power heated underwear for those long cave or mine dives.


Out of all the possible variations, there is at least one that fits you. The right primary light for you is one of ours. You will not go wrong starting small: upgrading later is a breeze. And a piece worn out after years of service can be easily replaced. Investing in the Agir light system means getting the best value for your money.

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Diver with jacket style BCD.

Jacket style BCD

At the dive centre, they hang on long racks, ready to be rented. The jacket style BCD comes in four sizes; small, medium, large and extra large. These four sizes supposedly fit all divers.

Almost every diver have used a jacket style BCD. The first time is usually during the SCUBA beginners course, be it PADI Open Water Diver, SSI Open Water Diver, NAUI Scuba Diver, CMAS Diver level 1 or any other similar training.

Buoyancy compensation device

The purpose of the BCD, the buoyancy compensation device, is to make the diver neutrally buoyant. Depending on body constitution, some people naturally float, others sink. When fully geared up, with an exposure suit, tank, fins, regulators and other equipment, most divers need some extra weight to stay neutral when the tank is nearly empty. The usual solution is a belt with lead weights, worn around the waist.

The extra weight that is needed for neutral buoyancy at the end of the dive likely makes the diver too heavy at the start of the dive, when the the tank is full. This is why the BCD is needed. It offsets the change in buoyancy.

Perfect fit

Thanks to the cummerbund and the adjustable shoulder straps, the staff or instructor can fit a BCD to a student in a few seconds. Just eyeball the rough size, put the BCD on, like a vest, tighten the cummerbund and pull the shoulder straps tight. Done. Off you go!

This is great for the dive centre staff. But maybe not so great for the diver looking to buy his or her own gear. Now it is not about it being usable by all divers. It is about finding something with the perfect fit for one diver. The diver is probably not exactly a size small, medium, large or extra large. Instead likely somewhere in between the four sizes. Maybe even smaller than the smallest or larger than the largest.

When buying a BCD for personal use it is more important with perfect fit than quick adjustment. It will only be used by one diver. With the BCD at home there is plenty of time to fine tune and adjust until the fit is perfect. Also, it is better if it stays the same over time, instead of constantly having to be readjusted.

Trim and streamlining

What about performance? While diving, trim and streamlining are two very important factors. Being streamlined and in trim saves a lot of effort. Reducing effort reduces gas consumption. Reduced gas consumption gives longer dives. Reducing effort also increases comfort. Increased comfort means better diving.

Divers in jacket style BCDs are often seen head up, feet down, out of trim. The design of the jacket style BCD, with a large air cell at the divers waist and sides, keeps the diver floating at the surface in a natural head up position. This is nice for the instructor who does not have to spend valuable time teaching students proper positioning in the water at the surface.

The better BCD

Glancing at the experienced divers, for example, technical divers, who seemingly without effort glide through the water in perfect trim carrying heavy equipment such as twin tanks and decompression cylinders. How do they do it?

It is not only training and experience. They have some help from their equipment. Nearly all of them use a backplate with a wing style BCD. The backplate has a harness, which can be adjusted to fit perfectly. The wing provide buoyancy exactly where it is needed.

The backplate

Backplate aluminium regular size
Aluminium backplate.

The backplate is a simple and inexpensive sheet of steel or aluminium, bent and shaped to be ergonomic. A steel backplate outlasts most diving careers. It can be severly mishandled by airport luggage staff or even be run over by a truck. It may get some scratches, but it will still work just like new.

The harness

Backplate stainless steel regular size
Backplate with harness.

The backplate has slots cut into it for a simple harness made of webbing, a belt buckle and some D-rings. Most harnesses also have a crotch strap to help keep the tank from sliding forward if the diver is in a head down position. The harness can be adjusted to fit its owner perfectly and the fit will not change.

It is put on and taken off just like any backpack. Arms go in under the shoulder straps and the webbing is closed around the waist with a buckle. When properly adjusted the fit is snug, not too tight, neither too loose, but just right.

The D-rings are used to attach additional equipment. For example the gauge, or SPG, is clipped to the left waist D-ring, where it is streamlined and does not dangle and reduces risk of entanglement.

The wing

Blackbird single cylinder 36 lbs wing
Single cylinder wing.

The modern wing is a donut shaped air cell made of a heavy duty fabric fitted with an inflator and a dump valve. It is sandwiched between the backplate and the tank.

It’s donut shape allows gas to move to where it is needed. When partially inflated it naturally wraps around the tank, making it streamlined. The buoyant force from the wing, placed on the diver’s back, around the tank, helps the diver achieve horizontal trim.

The heavy duty fabric resists wear and tear. However, should the wing be damaged it can easily be replaced. A torn and leaking jacket style BCD must be replaced with a new. The backplate and wing is modular. If one piece is damaged beyond repair, it is very easy to switch out for a new part.


Blackbird single tank rig 28 lbs stainless steel
Single tank rig.

A recreational diver looking to buy his or her own gear is searching for the best buy. Looking for the best piece of equipment for the best price available. Safety is very important. So is quality. Another factor is gear that can grow with the diver, staying relevant as training accumulates and experience is gained.

Diving in warm waters with a wetsuit? Snug the harness a little bit tighter. Want to switch to cold water and drysuit diving? No problem, no need to buy a larger BCD, just loosen the harness to fit the drysuit and the underwear. Want to carry a pony bottle for added safety during deep dives? Easy. Clip it to the left shoulder and hip D-rings. Oh, you want a twinset for longer and safer dives? Great. Switch the small single tank wing to a larger wing. Use the small wing for single tank diving in tropical waters and the bigger wing for the twinset. No need to get a new backplate and a new harness.

The limits of recreational diving stops you from going where you want to go? Thinking of technical diving. Maybe even cave or mine diving? You already have the rig you need. Big twinset, stage bottles, deco cyliners — maybe switch the wing for a larger one. Keep the rest.

Harness webbing starting to wear out? A worn jacket style BCD is difficult to repair safely. With a backplate, just buy 4 m of 50 mm webbing and replace it. Broken hardware? D-rings are cheap. No stitching required, just rethread the harness with new hardware. Lost a clip? Nooo problemo. They are easy to find at just about at every dive centre around the world.


Nearly all divers has some experience from using a jacket style BCD. Also, almost every diver that started using a backplate and wing style BCD never return to the jacket. Trust the evidence and testimonials of thousands of divers. Go for a backplate and wing. You will never want to go back.