Double Fisherman's Knot vs Water Knot
Life-safety notice
TyingPoint's illustrations are for learning. For any life-safety use — climbing, rope access, rescue, or load-bearing rigging — seek qualified in-person instruction, and always inspect and test every knot before you trust your weight (or anyone else's) to it.
| Trait | Double Fisherman's Knot | Water Knot |
|---|---|---|
| Family | bend | bend |
| Diagram steps | 6 | 5 |
| Life-safety context | Yes | Yes |
| Primary use | join two ropes | join two ropes |
Comparing these two only makes sense once you realize they were never actually competing for the same rope - one is built around round cord's ability to grip itself, the other exists purely because that same trick fails completely on flat webbing.
Put a double fisherman's knot in webbing and it won't seat correctly at all; put a water knot in round cord and it won't lock the way it does in flat material - so the real question this pair answers isn't which one is stronger in the abstract, it's simply which material is actually in your hands.
Both, tied correctly in their own intended material, test in a broadly similar 60-70% range, so raw strength rarely settles this comparison either way. Where the two genuinely diverge is in how much ongoing attention each one demands once it's tied: a double fisherman's knot dressed correctly in cord is close to a tie-it-once proposition for the rest of its working life, while a water-knotted webbing sling asks for a habit the fisherman's knot mostly doesn't - checking it before every single use, since folded webbing has a documented tendency to shift slightly under repeated flexing that round cord jammed against round cord doesn't share to the same degree.
Why you can't substitute one for the other
Tying a double fisherman's knot in webbing, or a water knot in round cord, isn't a matter of preference - the underlying geometry each knot depends on simply doesn't transfer. A water knot tied in round cord won't seat and lock the way it does in flat webbing; a double fisherman's knot tied in webbing won't grip the way it does in round cord. This is one of the few genuine either/or choices on this whole comparison list where the material, not the situation, makes the decision for you.
The maintenance difference that matters
Even correctly tied, a water knot needs a habit of inspection the double fisherman's knot mostly doesn't - checking that it hasn't crept, that the tails are still long enough, before every use it sees. The fisherman's knot, once tied and dressed correctly in cord, doesn't share that same creeping tendency to nearly the same degree.
The honest verdict
This one answers itself once you know what you're joining: round cord calls for the double fisherman's knot, flat webbing calls for the water knot, full stop. The real decision that matters is remembering to re-inspect a water knot before every use precisely because of its documented tendency to creep - a habit the double fisherman's knot doesn't demand nearly as urgently once it's dressed and set.
Why webbing behaves so differently from cord in the first place
It's worth understanding the actual mechanical reason these two materials need such different bends. Round cord, wrapped around itself, creates genuine friction across its full circular cross-section, and a knot like the double fisherman's exploits that by jamming two such wraps together under load. Flat webbing has almost no equivalent grip against itself when simply wrapped - it tends to slide flat against flat, which is exactly why the water knot's threaded-overhand construction, forcing the webbing to fold and bind against its own folded layers rather than just lying flat, is necessary in the first place. This isn't a minor technical footnote; it's the entire reason webbing and cord have completely separate join traditions rather than sharing one universal bend.
A habit specific to water-knotted webbing slings
Because of the water knot's documented creep tendency, many climbers mark the tails of a water-knotted sling with a permanent marker at the point where the knot currently sits, making it easy to spot at a glance during a pre-use check whether the knot has crept even slightly since it was last inspected - a small, low-effort habit that turns an otherwise subjective "does this look okay" check into something more objective and reliable. Even a small piece of colored tape at the same spot works nearly as well if a permanent marker isn't at hand, and it's a habit worth adopting the very first time a water-knotted sling goes into service.
Why some climbers avoid webbing loops entirely for critical anchors
Given the water knot's documented creep, some climbers deliberately favor cord and a double fisherman's knot over webbing and a water knot wherever the choice is genuinely open, specifically to sidestep the water knot's maintenance burden altogether. This isn't a universal rule - webbing has real advantages in bulk, cost, and abrasion resistance that cord doesn't always match - but it's a real, considered preference worth knowing exists rather than assuming webbing and the water knot are always the default choice.
A closing thought on making the right choice quickly
In the end, this comparison rewards simply looking at what's in your hands: round cord means the double fisherman's knot, flat webbing means the water knot, and the material itself removes any real ambiguity about which one to reach for.