A Santos Dive is named for my old friend Dennis Santos. It’s a dive that might include a certain amount of deviation from the plan made topside. And such leeway was why, having specifically said that I didn’t want to go into formal decompression, I was studying with interest the “Deco Required” display on the Shearwater Peregrine computer.
Shearwater Research is a Canadian company that was formed in 2004 to design computers for technical diving. Its machines have been aimed at open-circuit trimix and closed-circuit rebreather divers, and they are highly regarded.
Inevitably, with sophistication comes complexity and cost, and the brand had not crossed over into the less-demanding, more price-sensitive, computer-crowded recreational market.
With the launch of the Peregrine, Shearwater is now breaching that boundary, introducing a simplified and affordable three-mix air/nitrox computer with gauge function that carries with it Shearwater’s reputation.
Spoiler alert: The Peregrine is a very user-friendly computer, and that begins with the manual. It has a homely tone. It talks about “Erik” when referring to Erik Baker’s explanations of gradient factors for homework, conveying the impression that Shearwater is a small, hands-on company. It’s the best-presented dive-computer manual I have seen.
The Peregrine comes in a small zipped travel case. Even here we find attention to detail.
A form-fitted two-part hard-foam insert protects the computer from impact. The back of the insert is cut to house two Philips head screwdrivers for changing the wrist-strap for the supplied bungee cord. Even these have big grips for use with cold hands.
It’s powered by a rechargeable li-ion battery that charges wirelessly, so there are no charging sockets to flood, battery covers to remove or contacts to corrode. The charger connects to a USB lead.
Curiously, it doesn’t clip or use magnets to attach to the Peregrine, which you have to secure using the wrist-strap or bungee. Then it will stay connected even if you’re on a rolling boat.
The Peregrine is slim but with a decent-sized 60x40mm full-colour LCD QVGA screen. It’s inset to avoid scratches and an O-ring buffer allows you to set it down safely on its face.
Only two buttons are used to choose and set the functions, and you don’t need to employ those long or short presses in the right sequence to make and save your selection.
The Peregrine flashes up words such as Edit, Next and Save beside the button you need, so it’s very easy to follow.
The screen is neatly divided into boxes that clearly separate information such as current depth and elapsed dive-time from safety stop or, in deco, time to surface and ceiling depth, with a further box given over to the mix you’re breathing. The legends and numerals are very easily read.
The Peregrine uses the well-proven Buhlmann ZHL-16C algorithm. Unlike most ZHL-16C instruments, it doesn’t have a deep-stops option, although it does usefully let you choose the depth of your shallowest deco level from either 3 or 6m.
Setting 3 can be expected to clear faster because it will be the optimum depth in outgassing terms, but 6 provides more margin to recover control if you inadvertently ascend a little. Altitude adjustment can be set to auto or user-selected.
Like its competitors, the Peregrine allows you to select caution zones to reduce your gas-loading compared to running according to the standard parameters. Essentially you guess which of three safety levels best reflects your age, health and how cold or over-exerted you might get during your dive.
I experimented with this, setting the high conservative zone while using a different make of computer with the same algorithm that had made the same series of dives.
With that set to the least conservative setting, it allowed a no-stop dive while the Shearwater called for 17 minutes of decompression.
You can also change the gradients that the algorithm uses to calculate ingassing and outgassing. The manual warns against changing these unless you know what you’re doing, and refers you to Erik’s research, from which the protocols were adapted.
As a recreational diver I felt that warning hit me straight between the eyes and, for once, went with the advice rather than my usual instinct to meddle and see what happens.
You can set a specific time, such as three, four or five minutes, or select Adaptive for your safety stop. Adaptive takes into account whether you hit 30m or got within 5min of your NDL and adjusts the safety stop to 5min. Otherwise it chooses 3min.
Safety and explanation go hand in hand throughout the manual and set-up. You must deliberately opt into Multi Gas mode, for example.
If you set up for three-mix nitrox diving, using air as your bottom mix and switching to higher oxygen percentages (up to 100% O2 for the two deco gases) for stops, the manual warns that you’ll incur lots of extra deco if you don’t switch
to them when the Peregrine tells you to.
The Peregrine gives you a “simple” dive-planner so that you can see your no-deco limits for different gases, times and depths, as you might expect.
A separate full-decompression planner provides for calculating run-times or answering “what if” questions when you intend planned dives with stops. You can figure out the depths and times of stops for different bottom times, for example, including gas-switches plus how much extra deco might be called for if you’re forced to delay your ascent.
Deco-dive plan summary indicating that oxygen toxicity limit will be exceeded by 1%.
Enter your surface gas-consumption rate and the Peregrine also calculates how much gas you’ll need and adds that to the display.
You can save your plan and call it up under water for reference, which I didn’t have time to test. I wish I had – it sounds extremely useful.
Under water, the Peregrine also has a look-ahead feature that lets you see the additional deco you’ll run up if you stay at your current depth for a further 5min.
I’m fairly casual about going into limited deco, depending on whether I’m soloing or with a buddy I trust. The look-ahead feature allows you to plan on the fly.
It can also serve as a salutary warning of how much more deco just a few extra minutes’ bottom-time can rack up, encouraging you to pay attention to your gas-management.