“Shearwater Moves to 50/70 Gradient Factors: DepthPlanner’s DiveCommand Has Used It From Day One.”
Sep 30, 2026 · @scott fontecchio
Shearwater has raised the default GF Low on its dive computers from 30% to 50%. In plain terms: on decompression dives, your first stop will now show up shallower than it used to. If you only dive within no-decompression limits, nothing changes.
The new Tec mode default is 50/70 (it was 30/70). The Rec mode conservatism presets are now 50/75 (High), 50/85 (Medium) and 50/95 (Low). GF High, which controls how conservative you are at the surface, did not change on any setting.
The update is rolling out model by model, so it may not be on your computer yet. Check the release notes for your specific model before assuming what your computer is running.
Gradient factors in plain English
Your Shearwater runs the Bühlmann ZHL-16C decompression model. That model has a theoretical limit for how much dissolved gas your body can carry at each depth. Gradient factors let you stay a set percentage below that limit, so the two numbers are really two safety margins.
- GF Low (the first number) decides where your first deco stop is. A lower number means you stop deeper. A higher number means you start your stops shallower.
- GF High (the second number) decides how much margin you have when you surface. A lower number means longer shallow stops and a bigger cushion at the end of the dive.
A simple way to picture it: GF Low sets where your ascent staircase begins, and GF High sets how big the final steps are. Shearwater moved where the staircase starts and left where it ends alone.
The questions divers are asking
Does this change my recreational no-deco dives?
No. GF Low only comes into play once the computer puts you into mandatory decompression. If you stay within your NDL, your limits and ascent are exactly the same as before.
Which dives are affected?
Only dives that require mandatory decompression stops. On those dives, your first stop will usually appear shallower than it did at 30%. Total deco time and how stops are spread out can shift too, especially on deeper and longer dives.
Why did Shearwater make the change?
The thinking on deep stops has shifted over the past 15 years. A 2011 US Navy (NEDU) study found that a schedule with deeper stops produced more decompression sickness than a shallower one with the same total time. The logic is that time spent deep helps fast tissues but keeps slow tissues loading gas.
A 2023 study for the Belgian Navy made the point directly for Shearwater users. It found no evidence that the old 30/70 default gave safer decompression for air dives to 60 m, and that the deeper first stops it produced could actually add risk. A GF Low of 50 is a step toward that newer view.
Is a higher GF Low less conservative?
Not the way most people think. “Conservative” usually means more margin at the surface, and that is controlled by GF High, which did not change. A lower GF Low adds deep stops, and the research above suggests extra deep stops are not automatically safer.
Will my computer change on its own?
Only when you install the firmware update that includes it, and it is not out for every model yet. If you already set your own gradient factors, check them after updating. Confirm your numbers on the surface after any firmware update, not at your first stop.
I plan deco dives on software. Should I update my plan?
Yes. If your planning software is set to 30/70 and your computer now runs 50/70, the two will disagree about where your first stop is. Set both to the same numbers before the dive so the plan in your wetnotes matches what your computer shows.
Should I switch to 50/70?
That is between you, your training agency standards and your instructor. What matters most is that you know which numbers you are diving, you understand what each one does, and your whole team is running compatible settings.
Old vs new defaults at a glance
Only GF Low moved. Every GF High value is the same as before.
| Mode / setting | Old default | New default | What changes on a deco dive |
|---|---|---|---|
| Tec mode | 30/70 | 50/70 | First stop shallower |
| Rec, High conservatism | 35/75 | 50/75 | First stop shallower |
| Rec, Medium conservatism | 40/85 | 50/85 | First stop shallower |
| Rec, Low conservatism | 45/95 | 50/95 | First stop slightly shallower |
| Any mode, NDL dive | — | — | Nothing |
What to do before your next deco dive
- Check the release notes for your model to see whether the new defaults apply to you yet.
- Look at the GF numbers actually set on your computer after any update.
- Match your planning software to your computer’s settings.
- Talk settings with your buddy or team so everyone surfaces on a similar schedule.
- If you are unsure what numbers suit your diving, ask your instructor.
The short version: Shearwater nudged the first stop shallower on deco dives, left your surfacing margin alone, and did not touch no-deco diving. Know your numbers, and make sure your plan and your computer agree.
Sources
- Shearwater Research, customer notice on the new default GF Low (see the release notes for your model)
- De Ridder S et al., Selecting optimal air diving gradient factors for Belgian military divers, Diving and Hyperbaric Medicine 53(3), 2023
- Doolette DJ, Gerth WA, Gault KA, Redistribution of decompression stop time from shallow to deep stops increases incidence of decompression sickness, NEDU TR 11-06, 2011