Essential Knot Tying for Speargun Rigging: A Spearfishing Knots Guide

Introduction

If you spearfishing, the knot you tie is the only thing standing between you and a lost fish. It is not an exaggeration to say that a poorly tied knot can cost you not just your prize, but also your gear—a snapped shooting line or a lost shaft adds up fast. This spearfishing knots guide is for new and intermediate spearfishers who have moved past the basics and are ready to rig their own guns with confidence. I have seen guys show up to a dive with brand new gear held together by a single overhand knot. They were gone before lunch.

The wrong knot does more than just fail under load. It can jam in your muzzle, fail to release properly on a slip-tip, or abrade and weaken over time without you noticing. A good knot, by contrast, is a quiet confidence. You load your gun, aim, and pull the trigger, and you know the line will hold. That feeling is essential. Below, I’ll break down the knots you actually need, why they matter, and how to tie them so they stay tied.

Why Knot Choice Matters in Spearfishing

Knot failure in spearfishing is rarely a sudden snap. It is usually a slow failure—a knot that slips under a steady pull, frays because it was tied on dry line, or weakens because the tag end was too short and worked its way back through the twists. I learned this the hard way during a trip in the tropics. I was using a cheap pre-rigged setup on a bluewater gun. A medium-sized dogtooth tuna hit, took a solid run, and then the line went slack. When I retrieved the gun, the shooting line was still attached to the shaft, but the knot had slipped right off the mono leader. The mono was still on the reel. The knot just opened up.

That is what happens when you use a knot that is not designed for the material. Mono, especially heavy mono, is stiff and slick. Dyneema and spectra are slippery and have zero stretch. A uni knot that works fine on braid for fishing lures can fail on heavy mono under a big fish’s headshake. Saltwater also adds creep—knots that tied perfectly at home can loosen after a day in the water. This is not about breaking strength alone. It is about how the knot behaves under dynamic load, abrasion from the shaft slide, and the constant movement of the water. Every knot in your rig should be chosen with that in mind.

Tools and Materials You’ll Need for Speargun Rigging

You do not need a lot of gear to tie good knots, but you need the right stuff. Here is what I keep in my rigging kit:

• Mono line – 1.8mm to 2.0mm for most guns. Brands like Momoi or Jinkai are standard. Do not use bulk mono from a hardware store. It is not designed for this.
• Dyneema or Spectra – For wishbones and some breakaway setups. Use 1.5mm or 2.0mm hollow or braided.
• Crimps – For attaching mono to the shaft or slip-tip if you are not using a knot. I prefer copper crimps because they crush cleanly.
• Knot-tying pliers – These are a standout. A pair of quality knot-tying pliers makes tightening knots consistent. Your fingers alone will not cut it for heavy mono.
• A lighter – For melting tag ends. Butane lighters work best because they don’t leave soot.
• A small ruler or caliper – To measure consistent tag ends. Leaving the same length every time builds reliability.
• Saliva or water – Always lube knots before cinching. Saliva works fine. Water is second best.

Don’t fall into the trap of buying fancy knot-tying jigs or tools. They are unnecessary. A pair of pliers, a lighter, and your hands are enough. The brand of pliers matters less than your technique.

The Five Knots Every Spearfisher Should Know

You do not need fifty knots. You need five, and you need to know when to use each. Here they are:

1. The Breakaway Knot

This knot is for attaching your shooting line to the shaft. It is designed to release under tension when used with a slip-tip or breakaway system, which lets you ditch the shooting line and fight the fish on the main line. Key strength: it holds until you want it to release, then it opens cleanly.

2. The Bimini Twist

This is the strongest knot for heavy mono leaders (200lb+). It creates a loop that resists slipping, even under extreme loads. Key strength: it maintains nearly 100% line strength and is the standard for bluewater rigging. Time-consuming but worth it.

3. The Uni Knot

A reliable general-purpose knot for tying mono to swivels, crimps, or other rings. Key strength: easy to tie and reasonably strong for most fish up to about 30 pounds. Not for dyneema.

4. The Double Overhand Stopper

Used exclusively for speargun wishbones made from dyneema. Creates a stopper knot that prevents the wishbone from pulling through the muzzle band slit. Key strength: works with slippery, high-strength line.

5. The Surgeon’s Knot

For joining two pieces of mono of similar diameter. Key strength: fast to tie and good for light to medium game. Not as strong as the Bimini Twist but fine for reef setups.

Knot Comparison: Breakaway Knot vs. Uni Knot for Shooting Lines

These two are the main contenders for attaching your shooting line to the shaft. Here is how they stack up:

Breakaway Knot: This is my go-to for any setup where I am using a breakaway system or a slip-tip. The knot consists of a figure-eight or improved clinch tied around the shaft with a long tag end. When a fish hits, the knot releases from the shaft, leaving the shooting line free and letting you fight the fish on your reel or float line. Its biggest advantage is that it allows for quick changes. You can swap shafts or tips without re-tying the whole line. The tradeoff is that it is less bulky and can slip under light load if tied incorrectly. I have seen guys tie it with a too-short tag end, and it just pulls through. Leave a 3-inch tag, and you will be fine.

Uni Knot: This is a more permanent connection. It cinches tight around the shaft and does not release under load. It is more secure than a breakaway knot for direct-attach rigs where you want the shooting line to stay on the shaft. The downside is it is harder to untie, especially after being wet. If you are using a slip-tip that relies on the shooting line to release, a uni knot is a bad choice because it locks everything down. Best for: reef guns where you are shooting through fish and want the line to stay put.

If you are new, start with the breakaway knot. It is more forgiving and gives you the option to switch setups later. The uni knot is great if you know exactly what you are doing with a fixed-shaft rig.

Knot Comparison: Bimini Twist vs. Surgeon’s Knot for Leaders

This is where the strength game lives. Your leader connects your shooting line to your main line or breakaway setup. A failure here guarantees you lose the fish and potentially the whole rig.

Bimini Twist: This knot is the gold standard for heavy mono leaders. It creates a loop that is actually stronger than the line itself in many tests. I used a Bimini Twist on a 400lb mono leader when I chased dogtooth tuna in remote areas. One fish hit, took a 50-yard run, and the knot never budged. The Bimini is time-consuming to tie—I can do it in about three minutes now, but it took practice. what matters is to lube the line, twist slowly, and compress the twists before wrapping. It is not a knot to rush. For anything over a 30lb fish, or if you are using 200lb+ mono, this is your knot.

Surgeon’s Knot: This is the shortcut. It works for joining mono to mono of similar diameter, but it is significantly weaker than a Bimini Twist. I use it only for light game setups—reef fish under 20 pounds—or when I need a quick leader while on the boat. The surgeon’s knot is fast: two twists, and you are done. But I have had them slip on me when using 150lb mono for medium-sized amberjack. It is fine for a day of smaller fish, but do not trust it for a big dog or a tournament fish. If you are heading offshore, take the time to tie a Bimini.

Step-by-Step: Tying the Breakaway Knot for Speargun Rigging

Assume you have a shaft with a slip-tip or breakaway tab. You have your shooting line (I use 2.0mm mono). Here is how to tie it:

1. Pass the shooting line through the tab or tip eye. Start with about 3 inches of tag end. I always measure—too short is the most common mistake.
2. Form a figure-eight loop around the shaft. Take the tag end and cross it over the standing line, then bring it back under. This creates one figure-eight.
3. Repeat the figure-eight a second time. Go around the shaft again. This gives you two loops. Some guys do three, but I have found two is enough for mono up to 2.0mm.
4. Wrap the tag end through the center of the loops. Take the tag and make one or two wraps around all the lines inside the loop. This locks the knot.
5. Wet the knot with saliva. Not just a splash of water—saliva has a bit of give and lubricates better.
6. Pull slowly and evenly. Do not jerk. Use your knot-tying pliers on the tag end if needed. The knot should cinch tight against the shaft, leaving a neat loop around it.
7. Melt the tag end. Trim it to about 1/8 inch and melt with a lighter. Press it flat with a metal tool or your thumb (careful—hot).

Common mistake: pulling the knot tight before it is properly seated. If you pull too fast, the loops can twist, and the knot will not hold under load. Take your time. I have tied this knot in the water on a rocking boat, and it still works. Practice at home first.

Step-by-Step: Tying a Secure Bimini Twist for Heavy Mono Leaders

This is the big one. Use for leaders over 200lb. I use a Bimini for all my bluewater setups. Here is the method:

1. Find the midpoint of your leader. Pinch the line at this point between your thumb and forefinger. You want about 12 to 15 inches of tag on each side.
2. Roll the line between your palms. Keeping the pinch point stationary, roll the two tag ends together between your palms. They will twist into a braid. Aim for about 20 tight twists. The line should look like a twisted rope.
3. Bring the twisted section back toward the loop. Hold the twists together and separate the tags. You will see a small loop at the base.
4. Wrap the tag ends around one side of the loop. Take both tags and wrap them around one leg of the loop (not both). Do five to seven wraps, keeping them tight and even.
5. Pull the main tag end through the small loop. This locks the wraps. Now pull the standing part of the line (the leader) to tighten the knot. The loops should compress into a neat bundle.
6. Finish with a half hitch. Take the main tag end and tie a half hitch around the standing line. Pull tight. Repeat three times. This prevents the knot from slipping.
7. Trim and melt. Cut the tag ends to about 1/8 inch and melt. Do not melt into the knot itself—it weakens the line.

Troubleshooting: If the loop twists unevenly, you likely twisted the line incorrectly. Unwind and start again. what matters is to keep the twists tight and even. I use a pair of durable knot-tying pliers to pull the final cinch—it gives consistent tension. Do this on land first. It is a knot that takes practice but becomes second nature.

How to Make and Rig Speargun Wishbones

Wishbones attach your rubber bands to the gun. You can buy pre-made ones, or make your own from dyneema. I prefer making my own because I can customize the length and save money. Here is the process:

• Cut a piece of dyneema. Measure the distance from the muzzle slot to the wishbone groove on the shaft, plus 2-3 inches for the stopper knot. Double it because you loop the dyneema.
• Tie a double overhand stopper knot. Fold the dyneema in half. Tie a double overhand around both strands at the loop end. This creates a small stopper that sits in the band slit.
• Thread the dyneema through the band. Pass the loop end through the band’s loop, then bring the wishbone’s loop back over the band and tighten. This is the standard cinch knot for attaching wishbones.
• Test the length. The wishbone should be tight when the band is loaded—not slack, not under extreme tension. Adjust if needed.
• Check for fraying. After each dive trip, run your fingers along the wishbone. If you feel any fuzzy spots, replace it. Dyneema is tough but can abrade against the muzzle.

Pre-made wishbones are fine if you do not want the hassle. I keep a few spares in my kit. But DIY is cheaper and lets you dial in the exact length for your gun. Just do not rush the stopper knot—a bad one will pull through mid-dive.

Common Knot Tying Mistakes and How to Avoid Them

Even experienced guys mess up knots. Here are the mistakes I see most often:

• Not leaving enough tag end. A tag end that is too short will pull through or slip. For mono, leave at least 3 inches. For dyneema, 1 inch is usually enough. Measure until it is consistent.
• Tying wet line without lubrication. “Wet” is not the same as “lubed.” Saltwater can cause friction that damages the line. Spit on the knot before cinching. It sounds gross, but it works.
• Failing to heat-seal mono ends. A cut mono end is a sharp point that can fray or cut other knots. Melt it with a lighter until it forms a smooth ball. Press it flat for a clean finish.
• Using the wrong knot for the material. A uni knot on dyneema is a disaster. Dyneema is slippery, and the uni knot will slip out. Use a double overhand or a crimp for dyneema.
• Tightening too fast. Jerking a knot tight creates uneven tension. Pull slowly and steadily. If you feel resistance, stop and lube again.
• Overcomplicating it. I see guys using five knots where two will do. Stick to the five listed here. They cover everything you need.

Fix these, and your knots will go from “maybe” to “for sure.”

When to Replace Your Rigging Knots and Lines

Knots and lines wear out. You need to check them regularly. Here is my routine after every dive trip (or every two trips if I am lazy):

• Inspect the shooting line. Look for discoloration, stiffness, or fraying near the shaft connection. If the mono feels brittle or has nicks, replace it. A new line is cheap compared to a lost fish.
• Check the leader knots. Run your fingers over the Bimini or surgeon’s knot. If you feel any soft spots or the knot seems to be compressing unevenly, re-tie it. Leaders should be replaced every few weeks if you dive heavily.
• Test the wishbone stopper knot. Tug on it hard. If it pulls through the loops, it has worn. Replace the wishbone.
• Heed the smell test. If your mono smells like rust or salt, it is breaking down. Change it. I replace all my rigging at the start of each season, regardless of how it looks.
• Never rig in a hurry. If you are rushing to get on the water, you will tie a bad knot. Do your rigging the night before. Check it again in the morning.

Replacing your rigging before a big trip is cheaper than losing a trophy fish because a knot gave out. Do not skip this step.

Final Thoughts: Practice Before You Need It

Mastering these knots will not happen in a single afternoon. You need to tie them at home, on scrap line, until your fingers know the pattern. I keep a bundle of old mono on my desk and tie a Bimini while I’m on a phone call. It becomes muscle memory. When you are on the boat, in choppy water, with a fish on the line and time is short, you cannot afford to think about which way to twist. Your hands have to know. So practice. Grab some good quality mono line, a lighter, and your pliers, and tie each knot ten times. Then do it again. Take your time and get it right—it will make you a better, safer spearfisher. Ready to rig your speargun? Grab some mono and start tying.