Why Divers Should Bring a Jon Line

Why Divers Should Bring a Jon Line
Jon Line clip – won’t let you move up and down the rope.

It’s something of a rarity outside of the tech diving community.

Jon Lines are useful for anyone scuba diving from a boat or in strong currents.

Jon Lines are as simple as they are brilliant.

What is a Jon Line?

A simple piece of 3’ long nylon webbing with some form of karabiner in one end and a hook the other. It’s dirt cheap to make, weighs nothing, and can make deco or safety stops a breeze.

Originally, Jon Lines were used exclusively by technical divers, for doing prolonged decompression stops, sometimes in strong currents. But over time, they have been adopted by more and more recreational divers, too.

Some divers prefer to make their own, but Jon Lines can also be purchased commercially from most dive shops. The commercial ones will typically come with its own carrying bag that can be attached to a BCD D-ring.

Photo: Hiroyuki Saita
Photo: Hiroyuki Saita

Why do I need a Jon Line?

While ascending from a dive, and needing to do a safety or deco stop, scuba divers sometimes have to face strong currents, making it difficult to maintain the desired position near the boat.

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The typical way of handling this is for the divers to hold on to a downline or anchor line to make sure they can stay on position. But for popular sites, or large dive teams, the line can get very crowded.

If five or maybe ten divers all need to maintain the same depth for any given time. There’ll be quite a competition for space on the line to hold on to. And holding on in a strong current can get quite exhausting, especially in very strong currents or for prolonged stops, or both.

Enter the Jon Line

A diver will take out his or her Jon Line when starting the ascent or the stop, attach one end to himself, and clip the hook on the other end to the line.

This allows for the diver to move freely up and down the line, but constantly at the same distance to the line itself. This removes the strain of grasping on to the line and allows for more divers to be holding on the same line at the same depth.

Things to note when using a Jon Line

A few important things to remember about using a Jon Line: when not used, it needs to be securely stowed away in a pocket or similar. So it doesn’t drag along the bottom of the reef, and so you don’t risk entanglement.

Also, the hook on the end should be large enough to allow any vertical movement on the downline to not yank the diver up and down. This could be problematic from a DCS point of view.

The Jon Line is only intended to keep the diver in the same position in relation to the downline, not to tie him or her off on it. The depth is still supposed to be maintained by you using your own buoyancy skills.

The hook or karabiner that attaches to the downline should also be easy to remove if the diver suddenly needs to free him- or herself from the downline.

Have you ever used a Jon Line?

With all the advantages, the ease of use, and the low cost of a Jon Line, it should be standard equipment for all divers who regularly dive from boats.

Have you ever used a Jon Line on a dive with a strong current? Did it make the safety/deco stop easier? Comment on your experience.

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Bradley Axmith
Member
Bradley Axmith
Reply to  Trent

If it gives a greater sense of security, especially while you both garner a little more experience, it’s not a bad idea. You’ll be staying together anyway as a buddy pair. Consider where you’ll be diving though, and whether confined terrain (rock formations) might push you and your wife together with other divers. Take that into consideration during dive briefings and ask your divemaster or instructor–we’d suggest.

Trent
Trent

My wife and I are quite new to diving.

My wife finds it stressful trying to always know where I am and vice-versa. She basically wants to literally hold my hand the whole time. This is really restrictive as it leaves me unable to do much with my hands – even accessing the LPI can be problematic.

We’ve considered getting a Jon Line to secure to each other – we both have a knife and shears to free ourselves in the event the line becomes a snag instead of a safety line keeping us together – but taking away that constant holding of hands or endless scanning to keep sight of each other, probably makes us actually safer overall, than the small risk of entanglement, and it has the bonus of being able to be used in the normal way as well.

Fernando
Fernando
Reply to 

yes 3 min that in strong currents can feel like 30 min, as a tech diver and recreational diver i encourage divers to use it

Tracey Nicholas
Tracey Nicholas
Reply to 

Fail to plan, plan to fail. I always carry a knife, SMB, Torch, Jon line & reef hook irrespective of the time of day or conditions. A complacent diver is a dangerous diver. My safety gear stays on my BCD & in the same position so even blinded, I’d know exactly what area to reach for if/when it’s needed. That Jon line might mean the difference between life & death in a strong current for a fellow diver that’s unprepared or new to the sport.
I dive the Great Barrier Reef where conditions can change rapidly.

Stay safe & Happy Diving

Thomas
Thomas
Reply to 

I definitely agree that this isn’t something you should be hauling along on every dive, all the time. But I’ve had advantage of these on a number of occasions that weren’t tech diving, in particular in strong currents, or when there’s a lot of less-than-considerate divers around who don’t seem to respect that the person waiting at the 10 meters spot is probably waiting for the 5 meter spot to clear, but rather just jump in when they see their chance. 🙂

Martin
Martin
Reply to 

I don’t really see why divers should bring The Jon. It’s just 3 minutes we’re hanging there. If there’s a queue just hang back and wait the 3 minutes until the 5 meter spot is clear.
I can see it for tech guys hanging on for hours there it’s a big win. So no I don’t use one and I’m not planning.

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