The Case Against the Macho Dive Knife

When it comes to dive knives, many scuba divers make the mistake of buying a knife that is much bigger (and much more expensive) than they really need.  One of the cultural holdovers from the classic television shows which first popularized scuba diving is the image of the hardy, intrepid diver (usually male), with a giant knife on his weight-belt or strapped to his leg, ready to fend off dangerous predators underwater.  Consequently, a market has persisted for big, long, underwater knives, and equipment manufacturers are happy to provide them, often at what seem like exorbitant prices.

In reality, however, those dive knives with 8- and 10-inch (and even longer) blades are not at all ideal for most divers' needs.  In fact, there are many disadvantages to carrying such a large dive knife, and very little advantage.  In most cases, a small, blunt-tipped dive knife will be easier to handle, easier to affix to your gear, easier to access and much more useful overall than the huge knives ever would be. 

And for scuba divers who are willing to abandon the macho imagery of yesteryear in favor of something that works even better, there is actually a great alternative to carrying a dive knife altogether, which is more effective, more versatile, and amazingly, happens to cost less than even a small dive knife.

The likelihood of ever using a knife successfully to rescue oneself from an aggressive animal underwater is very slim.  This is primarily because animal attacks on divers are extremely rare, and in the few cases where they do occur, the incident will usually happen so fast that it's over before a diver would even have time to grab his or her dive knife, much less defend themselves effectively with it.  The real reason that scuba divers should carry a blade underwater is to be able to cut free of any entanglements that they or their buddy may encounter, and to have it handy in case of a medical emergency where it is necessary to remove an injured diver's equipment and exposure suit in a hurry.

For these real-world tasks, a set of trauma shears (aka EMT shears or Rescuer/Paramedics Scissors) is a much more effective tool than a dive knife.

Trauma shears can cut through a lot more than a dive knife can.  You can use trauma shears to cut a penny in half, and they can even cut through small metal cables.  Try doing that with your knife.  In addition, a knife can only cut through a line that is under tension, while trauma shears, because they are scissors, can cut a slack line or a taut one.

For emergency gear removal, trauma shears are even better.  After all, this is what they were designed for.  Although no one ever wants to be in this situation, imagine that your dive buddy is injured, and you have to get him or her back to the boat or onto shore to administer CPR or other medical care, but while you are trying to remove your buddy's gear, the clip to their BCD is stuck (I've actually had this happen, though thankfully, not during an emergency.)  How long would it take to hack through 2 or more inches of thick nylon webbing of the shoulder strap with your knife?  With a pair of trauma shears, you simply cut it in seconds.

Even if removing the scuba gear is no problem, the next thing you will have to do in an emergency is remove your buddy's exposure suit.  Regardless of whether they are wearing a wetsuit or a drysuit, cutting a diver out of a suit with a dive knife is not an easy task.  With trauma shears, you just grab the neck of the suit and start cutting.  In an emergency situation, every second counts, and wasting minutes trying to remove a wetsuit with a knife delays administration of CPR and other critical care, which could make a big difference in the outcome for your buddy.

There are a few tasks underwater for which a knife is more suitable than a pair of trauma shears, mainly involving prying small organisms from their substrates.  If this is your goal, then a small dive knife (with a blunt tip - not a pointed one) may be the right tool for the job.  However, even if that is your chosen dive activity, it still makes sense to carry a pair of trauma shears with you as well for entanglement issues or emergency gear removal purposes.  In addition, trauma shears meet the requirements for PADI courses which require a dive knife.

Trauma shears are widely available for less than $10 each.  Some scuba equipment manufacturers sell them with a nylon sheath that can be attached to your dive gear for easy storage and access during the dive.  Even though it does cost more to purchase them that way, I do recommend getting the sheath to hold the trauma shears.  If you ever drop your trauma shears, use them so much that the blade becomes dull, or dive with them enough that they start to rust, then you can just buy a replacement pair (without the sheath) from a medical equipment supplier for just a few dollars.  I usually buy a few pairs at a time, so I can have extras for my first aid kit, my toolbox at home, and my car, since trauma shears are so inexpensive and they're incredibly useful.  (They're also great for opening that plastic "clamshell" packaging that is so annoying.)

There's an old scuba joke about what the "real" purpose of carrying a dive knife is: if you're attacked by a shark, use the knife to cut your buddy and then swim like hell.  In reality, carrying a huge dive knife strapped to your body is unlikely to ever be useful for saving yourself from sharks, crocodiles or any other underwater attacker.  The only reason to carry one of those big knives is if you like the way it looks.  Trauma shears, on the other hand, outperform dive knives on most tasks,  and offer a lot of practical benefits for divers both underwater and on the surface.  For men and women divers who want to move beyond the impractical, macho dive equipment of the past, and carry a tool that offers superior performance to a dive knife, trauma shears are the way to go.