The folding dive knife is a relative newcomer to the scuba diving scene. This is due primarily to the fact that for a long time folding knives were generally made from a grade of steel that, while hard enough to hold a sharp edge, didn’t resist rust too well. The hinge pins and other moving parts that held them together were also susceptible to corrosion, so one giant-stride into the ocean could potentially ruin a folding knife’s ability to open and close properly.
Then around about 2004 the Spyderco knife company changed the game by introducing a folding or “pocket” knife with a new radical serrated blade that was razor sharp yet refused to rust. Since then, a number of other knife companies have jumped into the market with their own versions of folding knives that perform as well under water as they do on the surface.
The Upside to Pocket Knives
So what are the advantages of a folding or best dive knives? First and foremost, a folding knife, when closed, tends to be smaller and lighter and it stows easier than a fixed blade knife. The sharp blade edge lies protected in its handle cradle when not in use, allowing it to be carried in a pocket, hung from a lanyard or clipped to a D-ring. Yet when opened, a folding knife offers a blade length comparable to many fixed blade knives, as well as a full-sized handle for gripping. Also, folding dive knives are designed to be opened and closed with one hand and most of them lock in the open position, so using them couldn’t be easier.
Ricks Dive Center reached out to a number of manufacturers and distributors of folding knives designed for underwater use. Three companies responded with five models relatively new to the market. Following are what we discovered after subjecting each to a series of cutting and rust tests.
Best Dive Knives – RDC’s Dive Knife Breakdown
Fresh out of their boxes, we took each knife and first subjected them to a series of cutting tests using a variety of rope, cord and monofilament commonly used in the marine environment, and therefore what a diver might expect to encounter—and maybe get tangled in—while under water. This included: 1/2” nylon three-strand, commonly used for anchoring; 3/8” polypropylene three-strand, commonly used to rig lobster and fishing traps; 1/4″ Amsteel line, a very light but very strong braid used in place of wire rigging for some specialized sailboat applications; and, finally, 30-pound monofilament fishing line.
We first did a Loop test, where we made a large loop with each test line and, using an upward cutting stroke, counted how many pulls it took for a knife to make two pieces out of one. Then we did a Wrap test by coiling each test line tightly around a board, then counting how many slices it took to split the line using a downward sawing-type stroke.
It seems most divers tend to take care of their equipment, which usually starts with a good post-dive rinse. However, sometimes you just can’t do right by your gear, like when on a week-long live-aboard trip. To simulate such a scenario we submerged each knife in the ocean (one of our testers lives on a boat) three times a day for five days without a freshwater rinse. At the end of the simulated “dive trip” we inspected each knife for rust with Geraldo-like anticipation.
In a Nutshell
Overall, all our test knives were able to cut, hack or saw through whatever test materials we put before them; however, certain blade edges did better on certain materials, i.e. blades with wavy-edged serrations worked better on some materials than blades with pointy-edged serrations. Serrated edges of all styles worked great for snapping monofilament fishing line, while plain-edged blades tended to cut more efficiently through some of the rougher stuff. (See Cutting Chart for test results.)
When it came to rust, not too surprisingly, knives with titanium blades faired pretty well, as did blades made of H1 stainless. After a week of saltwater soaking we weren’t able to detect even a hint of rust or corrosion on these blades, nor on the bolts and pins that held them together. What did surprise us was how well the most budget-priced knife of the group survived a week of salty neglect. Read on for details and to check out the RDC Favorites.
Folding Knife Reviews
Mares Force Bat Titanium
The Force Bat Titanium is made of ultra-hard Beta Titanium which has all the benefits of regular titanium but boasts a 40-percent harder alloy. It’s strong, lightweight, and holds an edge, all without the threat of rusting. A small post on the top of the blade allows one-handed opening. The blade closes by pressing the indent on the back of the handle and folding the blade into its cradle. The handle is made of molded plastic and is curved to fit your grip. Jimping on the spine of the blade near the handle offers good thumb traction to prevent slippage while cutting. The blade has a combination half plain-edge, half wavy-serration. It comes with a carabiner and quick-clip for easy attachment to a BC D-ring.
Cutting Test Results
In the Loop tests the Force Bat cut through all materials with one stroke with the exception of the 1/4″ Amsteel, which required five pulls. The plain-edge section of the blade worked well on the nylon three-strand and the Amsteel braid, while the serrated section cut through the polypro and monofilament with minimal snagging. The Wrap tests required a few more swipes to get through each material since the combo blade edge had shorter sections of plain-edge and serration to work with than blades with either all plain-edge or all serration cutting surfaces.
The titanium blade on the Force Bat is strong, light and there’s no threat of rust. This combination of serration and plain edge, while offering less length of each cutting edge, gives the knife the benefit of having both. Throwing in a D-ring clip and other attachment hardware is a nice bonus.
Spyderco Atlantic Salt Yellow
Spyderco is known for bringing to the dive industry a new type of stainless-steel. Used on all Spyderco “Salt Series” knives, this stainless-steel, called H1, is a special alloy exclusive to Spyderco that uses nitrogen in place of carbon in its steel matrix. The result is a hardened material that holds a sharp edge while withstanding corrosion. This material is used on the knife’s blade as well as on all its internal components (pivots, clips, and screws).
The Pacific Salt Black Blade has a scalpel-sharp plain edge that’s coated black for a stealthy appearance. The Atlantic Salt uses Spyderco’s SpyderEdge super-aggressive serration on a Sheepfoot blade, which has a rounded tip (different from a traditional blunt tip). Mariners and emergency responders favor the Sheepfoot design since it has a sharp cutting edge but its rounded tip offers more safety when slicing close to soft parts. Both models come with fiberglass-reinforced nylon (FRN) Volcano Grip handles with titanium belt clips and holes for attaching lanyards.
Salt knives open easily with one hand using Spyderco’s trademarked “Round Hole” in the blade. Press your thumb into the Round Hole and rotate forward until the blade locks in place. To close, simply depress the indent on the handle while pressing the back of the blade (dull side) against something and rotate it closed.
The full-sized grips on these knives provide maximum blade control. The jimping (little dull serrations on the spine cusp of the blade) gives your thumb excellent traction, allowing you to apply significant downward cutting force without worrying about slipping. The Atlantic Salt also has this jimping feature on the underside of its blade, or the choil (where the index finger normally rests), providing excellent upward cutting control. The ambidextrous metal stowage clips on the handles work well for topside carry, but when under water we find it’s best to run a lanyard or split ring through the lanyard hole and clip it to your BC where it can be reached with either hand.
Cutting Test Results
The Salts dispatched our test materials without much effort. In the Loop cutting tests they both sliced through every line with only one pull, with the exception of the 1/4-inch Amsteel. The plain edge on the Pacific Salt Black took just two pulls to sever the Amsteel while the Atlantic Salt’s serrated edge took 10 pulls. This is because once the outer layer of the Amsteel started fraying, the sharp pointy serrations on the blade would snag. This was also the case in the Wrap cutting test where the plain-edged Black took only two slices to cut the Amsteel while the serrated Atlantic needed 10 cuts. However, the Atlantic Salt’s serrated edge excelled in cutting the 3/8” polypropylene line, requiring fewer pulls than the Pacific’s plain edge.
The plain-edged Pacific Salt Black cut through everything it touched without breaking a sweat. The Atlantic Salt worked best on polypropylene and lines with tight weaves. It also offered the best grip with jimping on both blade spine and choil. Both of these knives would be even more attractive if they came with sheaths or lanyards.
Unidive Titanium Folding Knife
The Unidive knife is all titanium, as in both blade and handle. The metal handle is wide and offers finger indents for maintaining a solid grip. The blade has a wicked pointed tip and offers a combination of razor sharp plain edge and pointy serration. There’s also a sharp line-cutting notch up next to the handle. An elongated hole in the top of the blade allows for one-hand operation. The blade locks open using a liner-lock, or leaf spring-type system, that butts up to the tang of the blade when opened. Press the leaf toward the handle and the blade can be folded closed. Jimping on the top of the blade gives a firm base to the thumb when bearing down on a cut.
The Unidive knife offers lots of attachment options. The knife itself has a metal belt clip and lanyard hole on the handle. It also comes with a sheath fitted with rubber straps that are designed to fit over the forearm but are long enough to wear on the calf as well.
Cutting Test Results
The Unidive was able to slice through all lines with two pulls except for the 1/4” Amsteel line, and that required 10 pulls. The plain-edge section was sharp with a nice belly that directed force to the cut. The pointy serrations, like the Atlantic Salt, got snagged while cutting the loose stuff. However, the monofilament line was snapped with one pull using smooth, serrated, and notch methods. Actually, the line-cutting notch is almost redundant on this blade, since the serrated edge does just as good a job of cutting through fishing line. And the notch eats up almost half an inch of blade length, thus shortening the length of the serrated edge, which in turn shortens the cutting stroke.
Its all-titanium build makes the Unidive an impressive looking knife that should last a lifetime. The sheath is an innovative solution for carrying the knife around at depth. Being able to mount it on either a forearm or calf makes it just that much more versatile.
This was a tough call. The Mares Force Bat is probably our top choice because of its rust-free titanium blade, combination of serrated and plain edges, both efficient cutters, and the fact that the knife comes with some nice attachment hardware, which saves us the hassle of coming up with a security system of our own.
Following the Force Bat would probably have to be the Spyderco Salts. We like how that H1 steel holds an edge and resists corrosion. Testers were split as to which blade type was best—SpyderEdge serration or razor-sharp plain edge—it really depends on your cutting application. But all testers agreed it would be nice if the knives came with a sheath or some kind of security system. Which is why you can’t count out the Unidive Titanium; it’s a nice cutter and it does come with a really nice sheath. However, we’d like to see the line-cutter disappear, you don’t really need it and it would increase the length of the combo cutting edge. And finally, don’t count out the Rescue Knife. It’s simple, offers no frills, but it cuts pretty darn good, and it’s only 20 bucks!
Cutting Test Results – Chart
|Loop Cut Test||1/2” Nylon 3-Strand||3/8” Polypro 3-Strand||1/4″ Amsteel Braid||30-lb. Monofilament|
|Spyderco Atlantic Salt||1 Pull||1 Pull||10 Pull||1 Pull|
|Spyderco Pacific Salt Black Blade||1 Pull||1 Pull||2 Pull||1 Pull|
|MaresForce Bat Titanium||1 Pull||1 Pull||5 Pull||1 Pull|
|ISC Unidive Titanium||2 Pull||2 Pull||10 Pull||1 Pull|
|ISC Rescue Knife||1 Pull||1 Pull||2 Pull||1 Pull|
|Wrap Cut Test||1/2” Nylon 3-Strand||3/8” Polypro 3-Strand||1/4″ Amsteel Braid||30-lb. Monofilament|
|Spyderco Atlantic Salt||3 Pull||2 Pull||10 Pull||1 Pull|
|Spyderco Pacific Salt Black Blade||2 Pull||3 Pull||2 Pull||1 Pull|
|MaresForce Bat Titanium||4 Pull||4 Pull||6 Pull||1 Pull|
|ISC Unidive Titanium||4 Pull||3 Pull||10 Pull||1 Pull|
|ISC Rescue Knife||3 Pull||3 Pull||5 Pull||1 Pull|
I’ve been a diving addict since my 14th birthday when my parents took me to the Bahamas and had my first scuba diving experience. I’ve been an active diver ever since but in the last few years my focus shifted on sharing my thoughts and experience on diving gear, writing product reviews and gave up on organizing dive tours.