CARRYING KNIVES WITH FIXED OR LOCKING BLADES of more than 7.5cm long is illegal, unless you have reasonable excuse or good reason. If you are going diving, or have just returned from buying a knife, it is unlikely that an offence has been committed.
But if you have just been diving, have taken off most of your kit but are still wearing your knife strapped to your leg, you could be in breach of the Criminal Justice Act 1988, Section 139.
So before going for that butty, stow your knife securely away with your BC and fins.
Why do we carry a knife In the old days, standard-dress hard-hat divers went into the water with big brass-handled knives strapped to their chests, in case a tether or safety-line got entangled. These knives were like bread-saws, because they had to be able to slash through stout hemp rope.
Tradition dies hard, and often the first item of kit new divers buy is a massive shiny-bladed knife. Its a pity so few are good for getting you out of trouble! Your problem is more likely to be abandoned fishing net or hard-to-see monofilament line than rope.
If you are ever trapped in the invisible embrace of fishing line, you need to be able to access your knife easily - and you may not be able to reach your leg or to slash away at the line or net.
Some divers suggest that you put air into the BC to make yourself positively buoyant in such a situation, drawing the line taut and making the knife or cutter more effective. Dump the air as soon as you are free.
Usually knives with blades equipped with line-cutters are essential for doing just that. Knives that can double as screwdrivers, bottle-openers, fruit-peelers and shackle-wrenches are useful, too. They are never weapons, they are tools.
Sheath design is important. I have never had to buy a knife because Ive found so many lying on the seabed.
We asked all the major dive gear distributors to send us a selection of their knives and cutters. One surprised us by saying that he was reluctant to do so. When asked why, he replied: All the knives we sell are crap!
It is true that most knives are sourced from the same cutlers in Italy or the Far East, and some of the cheaper ones are exactly that - cheap.
Many of those featured here come with various blades. They can be chisel-ended or pointed, have a slicing blade, a serrated blade for sawing through rope, and a built-in line-cutter for slashing through net. Some have additional features. Consumers demand rust-proofing. Alas, the better the rust-proofing of stainless steel, the less easy it is to hone to a sharp edge. Its a matter of compromise.
Clean a blade after diving and oil it well before storing, and it should last many years. If you want a lightweight, sharp, rust-free blade, fork out for a titanium one.
Line-cutters that use a simple box-cutter blade usually need a new blade often because of rust, but they are cheap. Dedicated line-cutters are hard to cut yourself with, and cut monofilament line easily, but they are useless for opening bottles and making sandwiches!
We live in a one-market economy, so you may well find knives exactly the same as those listed here, but bearing different marques.
We tested each item by cutting both a length of 1.5cm-thick heavy-duty rope and a stretched length of fishing line, and decided if cutting each was difficult, average or easy (rated 1 to 3 in each case). We also rated each knife on how easy it was to extract it from its sheath or other fixing point, and how secure that sheath was (0 = extremely difficult, 3 = good).
Where there was a choice of blade type, we chose what we thought was the most likely best-performer for this task. Each knife is rated against others in the same group, and listed in descending order of effectiveness.

Standard Knives
These are popular knives with blades 11-12cm long. Striking similarities among this bewildering array of lethal weapons often indicate a common source. All have both slicing and sawing edges, and all but one have a line-cutter built into the blade. However, we found that often fishing line got caught in the larger serrations of a blade, making it difficult to deal with.
We preferred those few blades in which the line-cutter was incorporated on the slicing edge. We only rarely encountered difficulty releasing a knife from its sheath, and all had anatomically efficient handles. Choose whether you prefer a point or a chisel end.

1. UK Blue Tang Hydralloy Blunt£27 US chisel-ended knife dealt well with thick rope and fishing line by slashing at it, but there is also a line-cutter in the slicing edge of the blade. Locking sheath functioned well. Hydralloy seems to be an alternative name for a grade of stainless-steel. 3/3/3 [Best in Class]
2. Beaver Assassin£35 Coloured blade of this all-black knife incorporates a bigger line-cutter than some of its rivals and its effective. Sawed through rope easily too. Less easy to access from its sheath than some. 3/3/2
3. Cressi-sub Norge£23 Standard design. Made in Italy with grippy rubber-covered handle and easy-to-access sheath. 3/2/3
4. Wenoka Big Squeeze£50 Delightful action to sheath-lock mechanism provides easy access to this slim yet robust knife. Made quite short work of both rope and fishing line. 2/3/3
5. Apollo TAS Blade£60 Expensive yet simple. Made in Japan. Two types of serration. Dealt with fishing line easily. Locking sheath was secure but difficult to release the knife from. 3/3/1
6. IST K11£23Heavy-duty serrations on saw edge tended to tangle with fishing line but it made short work of rope. Locking sheath average. Chisel end. 3/2/2
7. Scubapro K5£36 Day-Glo yellow fittings distinguish this knife from similar Italian-made rivals. Suffered from same line-cutting problems as other Bowie-style knives described below. 3/1/3
8. UK Blue Tang Titanium£57Did not deal with thick rope as well as cheaper Hydralloy sibling but cut through fishing line like butter. Rust-free and lightweight. Sheath works like a dream. 2/3/3
9. Oceanic Saracen Bowie£25 Useful knife in Bowie style that could do with line-cutter being on the smooth side of blade, away from very coarse serrations designed to saw through thick rope. 3/1/2
10. Seemann-sub SK20£23Another Bowie-style knife that had problems dealing with fishing line because of coarse serrations of its sawing edge. Standard locking sheath. 3/1/2
11. TUSA X-pert TG£40Comfortable rubber-covered handle fitted with blade with both slicing and sawing edges. We encountered tangling with line-cutter because serrations next to it were so large. 3/1/2
12. Beuchat Maximo£40Made in France. Hard-to-find line-cutter. Hacked through fishing line and thick rope with another part of the blade. Handle has Day-Glo insert. Sheath secure once mastered and knife is inserted right way round. 2/2/2
13. Mares Skorpio Drop Point£44Effective yet simple blade with rubber-covered handle in almost impossible-to-use sheath. 3/2/0
14. Technisub ZAK 3£30Impressive-looking. Wide jaw line-cutter, chisel-ended blade with two types of serration. Shackle keys of two sizes. Did not seem very sharp - luckily, as it was a struggle to wrench from its sheath! 2/1/1

Outsize Knives

If a standard knife is not considered big enough, try one of these, with blades of more than 13cm in length.

15. IST K10£23 Standard design from Taiwanese cutlers but worked excellently. Knife both secure and easily retrieved from hard plastic holster. 3/3/2 [Joint Best in Class]
16. Seemann-sub SK9£23. Exactly as IST K10 above. 3/3/2 [Joint Best in Class]
17. Oceanic Blunt Tip£24Purposeful chisel-ended knife with serrated edge and line-cutter on one side of blade. Useful tool with sheath to match. 3/2/2
18. Poseidon Mini Master Blunt Tip£48 Cool steel - an uncluttered blade cuts without a hitch and the chisel end combines with striking point for serious effect. Not convinced of sheath reliability. 3/3/1
19. Poseidon Mini Master Pointed Tip£43 Pointed version of blade above. 3/3/1
20. TUSA Imprex Blunt£48 Heavy stainless-steel blade can be honed to very sharp edge. Chisel end. Made short work of rope but struggled a little with fishing line. Sheath very effective. 3/1/3
21. Cressi-sub Orca£37 Big, heavy, calibrated measuring blade, worked surprisingly well. Pity the rubber loop that keeps it in its sheath will eventually break. 3/3/0
22. Technisub Diablo Pro£43 Diabolical to free from sheath, but sawed through rope and slashed through fishing line without much problem. Two different-sized shackle-keys included. 3/2/1
23. Beaver Sceptre Titanium£52 Lightweight and rust-proof so looks the part, but not very effective at cutting rope or fishing line. 1/1/3
24. Technisub Diablo Tool£47 Good rope and line-cutting abilities with serious-looking chisel-ended blade that includes shackle-key for sailors and two common-size open-ended spanners. Resulting blade so complicated that it tended to tangle when slashing at fishing line. 3/1/1
25. Typhoon Pulsar£23 Looks like a sword and could see you out of trouble. Larger serrated side of blade seemed ineffective but theres enough left to do a good job and the line-cutter is unaffected by being close to it. Old-fashioned rubber loop holster lets it down. 3/2/0
26. Markat Commercial Knife£18 Feels cheap and is, but you can almost fence your way through entanglements. Rubber-loop sheath poor. 3/1/0
Small Knives
For BC or belt-mounting handily high on your body, these knives promise to get you out of those tangles that might make a knife on your calf hard to reach.27. Seemann-sub Titanium Folding£85 You get what you pay for (in this case a lot). Did everything well, though not easy to fold up. 3/3/3 [Best In Class]
28. Cressi Lama£25Not the sharpest but can do the job. Securely stows and unstows readily from sheath. 2/2/3
29. Oceanic Cutter£13Reminiscent of UK Remora, remarkably effective on both rope and line and stows easily in webbing/Velcro pouch. 3/3/2
30. Ralf Tech WR1£75 Also available in stainless steel (38), this titanium knife cut rope easily but was not so good with slicing fruit! We struggled a bit with sheath and it took effort to cut fishing line. 3/2/2
31. Mares Zorro£35 Easily attached to any webbing, heavy-duty fabric holster uses a lot of Velcro. Sawed through rope very well but beaten by tangled fishing line. Pointed end makes it weapon-like. 3/1/3
32. Scubapro Folding Knife£45Reintroduced by popular demand, slices and saws but almost useless on fishing line. Perfect stowage in simple fabric holster. 3/1/3
33. Seac-sub Rip Series£45 Attractive, each version has a specialised blade of German steel. Rip Tek good for slicing and has three shackle keys. Rip Line copes well with rope. There are others, and you would really need the set. Each little sheath proved excellent for accessing and security. 3/1/3
34. Seemann-sub SKT£50 Titanium, so lightweight, strong and long-lasting. Grippy handle. Made short work of rope, though struggled a little with line. Webbing-style sheath excellent. 3/1/3
35. Markat Shark Knife£13 Cheap and cheerful, uncluttered blade more effective on line than expected. Stowed crudely but effectively. 1/3/2
36. Oceanic Spinner£22 Quite useful for cutting rope and eventually made progress with line, but quite hazardous withdrawing from sheath. 3/2/1
37. UK Remora£27 Cuts rope and slashed easily through line. Would be a winner if not for danger of cutting yourself extracting it from sheath. 3/3/0
38. UK Trigger£23 You would be out of air long before remembering how to get this out of its spring-loaded sheath, if it hadnt already been knocked and gone missing. Cut both rope and fishing line if you used main blade and ignored line-cutter. 3/2/0
39. Wenoka Squeeze Lock£46 Not very sharp. Needed to hack rather than cut, but delightful in how it stows in its sheath. 1/1/3
40. Spora-sub Mini Snake£27 Cruel-looking blade did better with fishing line than with rope. Rubber-like sheath will attach to any webbing but knife secured by old-fashioned rubber band that may not last. 1/2/1
41. TUSA FK11 Mini£30 Not big enough to saw thick rope, easily tangled in fishing line, disappointing. Sheath efficient and secure. 1/0/3
42. Scubapro K3£36 Sort of knife found in the best Christmas crackers, it cut rope and line but with some difficulty. We enjoyed looking for it after it had been improperly stowed. Screwdriver end proved useful. 1/1/1
43. Seemann-sub SK30£15 Not good at cutting rope or line. Insecure in sheath too. 1/1/1
44. Technisub Mini ZAK Beta£28 Maker must have come up with this after discovering how useless Alpha was at cutting. Useful screw-driver end and shackle-key but made heavy weather of any serious cutting. 1/1/1
45. Markat Buck Folding Knife£26 More a boaters knife than for a diver, cuts through rope easily but made little impression on monofilament line. Sheath did not look secure for use underwater but had grippy handle. 2/0/0
Heavy Duty Shears and Multi-Tools
These are the tools of serious underwater escapologists. Some incorporate both types of knife blade, slicing and sawing.

46. Aqua-Lung Cisor£60 Multi-purpose tool promises to do everything well. Shorter blade of scissor-action made it slightly awkward when battling with fine line. Excellent sheath. 3/2/3 [Joint Best in Class]
47. Coltri-sub Pacific Shears£37 Its a knife, its got a scissor-action, it slices, saws and cuts line. Rubber-covered handles very grippy. 3/3/2 [Joint Best in Class]
48. IST Shears£16 Secateurs for divers! Equipped with a saw-edge, but did less well cutting rope. 1/3/2
49. Mares Fiskars Scuba Scissors£23 Inappropriate for cutting rope. Simple but well-made shears would see Steve McQueen happily through barbed wire. Supplied in webbing/Velcro holster that can be attached almost anywhere. 0/3/3

Simple Shears and Line Cutters
These implements are intended to do just that - cut line. Monofilament fishing line is a real hazard near wrecks and other popular fishing locations, and line-cutters are usually simple box-cutter blades contained within a large plastic mount.
50. Dive Rite Z Knife£10 Small, unobtrusive, secure pouch fits on any webbing. There when you need it, with useful finger-hole so you dont drop it. 0/3/3 [Joint Best in Class]
51. DiveRite Trauma Shears£11 Handy for snipping away at any line or netting, but dont expect to do anything else with these. You cant even cut yourself! 0/3/3 [Joint Best in Class]
52. Buddy Line-Cutter£8 Designed to stow in a BC pocket, retrieved by lanyard and toggle. OK performer. 0/3/2
53. Beaver Pro Net-Cutter£7 Sold with separate pouch that was not very good. Could get you out of an entanglement 0/3/1
54. Beaver Pro Line-Cutter£8 Nothing Pro about cutting yourself free, but this heavier version does the job. Optional pouch not very secure. 0/3/1

Alpha Distribution (01709 515157) for Seac-sub
AP Valves (01326 561040) for Buddy
Aqua-Lung UK (0116 212 4200) for Technisub
Beaver Sports (01484 512354)
Blandford Sub-Aqua (01823 663849) for Mares and Spora-sub
CJ Evans (01258 451269) for Apollo
CPS Partnership (01424 442663) for TUSA
Cressi UK (01484 310130)
Denney Diving (01642 486666) for Ralf Tech
Markat (01935 815424)
Oceanic SW (01404 891819)
Poseidon Diving Systems (01420 84300)
Sea & Sea (01803 663012) for DiveRite, IST and UK
SubmarineManufacturing (01772 687775) for Coltri-sub
Swan Co (01964 532202) for Seeman-sub
Typhoon Int (01642 486104) for Typhoon and Beuchat