A Tackle Shop Guide to Dive Knives
The main confusion we see with dive knives is people thinking they are just for scuba divers. The truth is, for many spearos and boat owners, a good knife is a straightforward safety tool. But the single biggest complaint we hear in the shop has nothing to do with sharpness—it’s about rust. Understanding why they rust, and how to choose one, is the key.
A Note From Our Local Experts
"The number one complaint we get on dive knives is rust. A customer will come in and say, 'I bought this stainless steel knife, and it’s rusting already.' It’s a very common frustration. The hard lesson people learn is that 'stainless' does not mean 'rust-proof,' especially in salt water. They are two different things. A knife will last if you maintain it, but even a good one will corrode or show signs of pitting if you put it away wet. Rinsing and drying your diving knives is the most important part of owning one.
That said, we stock some high quality knives that are made from 420 stainless steel to improve the longevity of your knife. In my years of experience in the industry I have found that some of our best sellers come from the Land & Sea brands with the Buddy knife being the most popular"
- Ben Czulowski, Owner, Fishing Tackle Shop (Ocean Storm) | 20+ years industry experience
Dive Knife vs. Fishing Knife: What's the Difference?
Each style of knife has a design fit for a different purpose: A fishing knife is for cutting bait and filleting; it has a thin, flexible blade and a simple sheath. A dive knife is a safety and utility tool. Its blade is usually thicker and stronger, designed for cutting rope or dispatching fish. More importantly, it comes with a locking sheath and leg straps so it’s securely attached to you if you end up in the water.
Blade Features: What You Actually Need
You'll see a few different blade styles. Here’s a simple breakdown:
- Edge Type: A knife with a serrated (saw) edge is what you want for safety. A serrated edge is far better at cutting through rope, netting, or tangled fishing line than a plain edge is.
- Point Type: You'll see sharp 'stiletto' points and blunt 'chisel' tips. The sharp point is useful for spearfishing to dispatch a fish. The blunt tip is a popular choice for boaters as it's safer to use on a moving boat and the hammer tip is ideal for divers who like getting abalone.
- Line Cutter: Many knives include a small, sharp notch near the handle. This is a dedicated line cutter, perfect for quickly slicing through fishing line without having to use the main blade which could be slighly less effective.
The #1 Problem: How to Stop Your "Stainless" Knife From Rusting
As Ben mentioned in the note, all stainless steel will eventually rust in a saltwater environment. The fix is simple maintenance, but you have to do it every time.
- Rinse it Thoroughly: After every single trip, take the knife out of the sheath and rinse both parts with fresh water.
- Dry it Completely: Don't leave it to air-dry. Wipe the blade and handle down with a cloth.
- Store it Dry: Store the knife out of the sheath to let everything air out. If you're storing it for a while, wiping the metal blade with a bit of food-grade silicone (like Inox) will give it a protective film.
Frequently Asked Questions
Why are most dive knives made of 420 stainless steel?
That's a great question. It's all about a trade-off. 420-grade steel has very high corrosion resistance, which is what you want for a knife that's always in salt water. It may not hold a razor-sharp edge as long as a premium kitchen knife, but it's tough, easy to re-sharpen, and does the best job of resisting rust for the price. It's the right balance for this type of tool.
Why can't I get an abalone off a rock easily? What's the best tool?
An abalone's foot has incredible suction. You need a tool with a broad, flat tip that can be wedged underneath it. Many of our dive knives, like the Buddy and Commando, have a blunt chisel tip that is designed for this. A sharp, pointy knife is the wrong tool and very dangerous for this.
What's the difference in sheath locking mechanisms?
There are a few styles. Some are a simple friction-fit, some have a loop-over 'O-ring' or rubber strap, and some (like the Buddy) have a 'push-button' positive lock. The push-button lock is very popular as it gives a confident 'click' so you know it's secure, and it's very fast to release with one hand.
Why choose a bright fluoro knife over a black one?
This is purely a practical choice. A black knife looks tough, but a bright yellow, orange, or green handle is far easier to see if you drop it on the boat deck or on the sea floor. For a safety tool, being able to find it in a hurry is a big advantage.
How do I properly attach the sheath to my leg?
The most common way is to mount it on the inside of your calf. This helps prevent it from getting snagged on boat ladders or lines. Run the straps around your leg, making sure they are firm but not cutting off circulation. Always position the handle so it's easy for you to grab.
Can I use my dive knife to pry open oysters?
We strongly advise against it. A knife blade is not designed for that kind of hard lateral (sideways) prying. Using the tip to pry or chip at things is the fastest way to snap the point off, which is not covered by warranty. A dedicated oyster shucker is the right tool for that.
Can I stop a shark attack with a dive knife?
No. You should never, ever rely on a small knife as a shark defence. It is not an anti-shark tool. In an absolute worst-case, life-or-death situation it's better than nothing, but its true job is as a utility tool for cutting line, rope, or dispatching a fish you've speared.
The serrated edge on my knife is dull. How do I sharpen it?
To be honest, for most of the knives we sell, it can be a time consuming process. It requires a sharpening tool like a diamnond sharpener rod and a lot of time. Given the practical price point of most dive knives, many customers find it easier and more effective to simply replace the knife once the blade has passed its peak performance.
Is a knife or a dedicated line cutter better for my boat?
For pure emergency safety on a boat—like cutting a prop free—a strong knife with a serrated edge is a great all-rounder. However, many boaters now also keep a dedicated 'hook' style line cutter or a pair of safety shears handy. They are often safer and faster for cutting tangled line in a panic.
