Your shot limit is determined by your visibility. No matter how powerful a speargun you have, it is useless if the fish is invisible at the length that your speargun is powerful for. Visibility must therefore determine your structure and gear, in turn determining your barrel length, band configuration and more.
Clarity, terrain and the target species determine the suitable barrel length, band setup, shaft and the rest of the scuba diving speargun equipment.
Reading visibility as an effective range budget
In many cases people treat visibility as a number (8 metres for example) rather than as a budget. In practical terms what this means is that if you can see a fish at 8 metres then in practice you have about 5-6 metres of effective shooting distance before the fish leaves the area. This is because it takes time to track the fish, line up the shot and fire the harpoon. A speargun that shoots well at 12 metres is of no use in this type of water.
The clarity of the water will change over the course of the dive. A thermocline, a patch of run-off or even the stirring of sand up from the bottom can suddenly change the perceived clarity of the water at twenty metres down. Use the water as it is at the depth at which the fish are holding.
Matching barrel length to the window
- Under five metres visibility, a 60cm to 75cm gun keeps the muzzle inside your line of sight and lets you swing fast in tight quarters.
- Five to twelve metres, a 90cm to 100cm gun covers most reef work without becoming unwieldy.
- Beyond twelve metres, 110cm and up starts to earn its keep, particularly on open sand, drop-offs and pelagic hunting.
Structure dictates manoeuvrability more than clarity does
Clear underwater in a cave? Shoot short. Solid structure, like a reef, determines how much space you have to shoot a fish, reload your speargun, and get off another shot before the fish passes through the coral with your shaft.
On broken bommies and isolated ledges, a short-bodied ‘reel’ speargun with 2 bands can penetrate deep into fish residing in deep crevices within the reef system. On open bottom however, this same ‘short’ speargun will not possess the sufficient penetration to kill at range, despite the target species being clearly visible at distance.
The trade-off nobody escapes
Longer barrels have longer band stretch which results in higher shaft speed and better tracking. However, shooting at long range can be slower as it takes more time to target and acquire aim. Shorter barrels shoot quickly but have the reverse effect of longer barrels. It is up to the diver to decide which of these negative traits are more desirable than the other on any given day.
Target species and shaft selection
As far as species are concerned, it is the shaft’s diameter and rigging which determine what sort of shooting you are able to do. A 6.5mm shaft has plenty of mass to deliver its momentum to larger fish, but needs more power in its bands to propel it, hence a longer gun or possibly a triple band setup. In contrast, a 6mm shaft is light and powerful allowing for fast shot placement on the smaller, highly mobile reef species.
When considering the type of line to attach to the reel, remember that species that will charge into cover or swim off into open water need floatlines with slide rings. Fish of the reef, shot within metres, are usually to be subdued before they can swim into structure.
A practical matrix for common conditions
| Condition | Barrel length | Bands and shaft | Line setup |
| Green estuary or surge zone, 2 to 4m visibility | 60 to 75cm | Single 16mm band, 6mm shaft | Reel, short line |
| Coastal reef, 6 to 10m visibility | 90cm | Two 16mm bands, 6.5mm shaft | Reel or short floatline |
| Deep ledges and drop-offs, 15m plus | 110 to 120cm | Two to three bands, 7mm shaft | Floatline with slide ring |
| Blue water pelagic | 130cm plus | Three bands, 7.5mm shaft | Break-away, bungee, float |
Building a two-gun kit
Divers who explore varied coastlines are generally best served by owning two purpose-built spearguns instead of one gun that attempts to compromise. A short reef gun and a longer open-water gun allow for more realistic choices on a given day. Make sure both guns have the same diameter shafts and same band dimensions so that you can use the spares on the other as well.
Adjusting the rest of the kit
Low visibility requires a low-volume mask with a wide field of vision to be able to see the full circle of water in front of you. Dark or reef-patterned wetsuits are best used in green water while blue or open-water patterned suits are best used in clear water.
- Reassess visibility on the first descent, not from the boat.
- Rig the gun that suits the layer where the fish are holding.
- Carry a spare shaft matched to that gun, not the other one.
- Shorten floatline length in structure to reduce entanglement.
If you treat all of the scuba diving gear as specific decisions that you can make based on what the water is doing on a day by day basis, you will find that the equipment ceases to limit your diving.
