IT WAS REMISS OF ME not to have taken a look at this diving computer sooner.
I suppose I’d been put off by those technical diving computers that need you to get your head inside the head of the guy who wrote the software for them.
After several long-distance trips where all I could get were not-very-helpful displays such as “Missed Stops – Use Tables”, such esoteric instruments had lost their appeal for me.
Of course, I was aware that many closed-circuit rebreather manufacturers had adopted Shearwater instrumentation, but none of them had CE-certification, and the policy at DIVER HQ was that I was to concentrate my efforts on those that had, because they’re the ones you can buy and resell in the UK.
Then the CE-certified JJ-CCR came into my life, and all that changed. There was a Shearwater Predator, sitting loud and proud on my wrist, and it was a revelation of simplicity to understand and clarity to read.
So I got on to Bruce Partridge at US-based Shearwater Research and berated him for never having sent me one of his computers before. He was good-natured enough not to point out that I had never asked before. Within a short time I was unwrapping a parcel with an open-circuit version of the Shearwater Predator inside.
Now, because Shearwater Research reserves the right to constantly update and upgrade its products, I should explain that the computer I had was the Predator PROT-SA version 200A037, just in case the one you already have or may be looking at is different. It is suitable for open-circuit trimix and nitrox diving.
Bruce is very upfront about his products. All computer manufacturers will include a legal disclaimer that their product cannot unfailingly prevent decompression injury, but Bruce goes a little bit further.
It’s refreshingly honest. This is just one excerpt of what he includes with his products:
“Warning. This computer has bugs. Although we haven’t found them all yet, they are there. It is certain that there are things that this computer does that either we didn’t think about, or planned for it to do something different.
“Never risk your life on only one source of information. Use a second computer or tables. If you choose to make riskier dives, obtain the proper training and work up to them slowly to gain experience.
“This computer will fail. It is not whether it will fail but when it will fail. Do not depend on it. Always have a plan on how to handle failures. Automatic systems are no substitute for knowledge and training.
“No technology will keep you alive. Knowledge, skill, and practised procedures are your best defence. (Except for not doing the dive, of course.)”

The Algorithm
The Shearwater’s basic decompression algorithm or mathematical calculation is the well-used Buhlmann ZHL-16C, which is available in the public domain. It has been modified to incorporate gradient factors developed by Eric Baker.
The default of the system is 30/85, but this can be adjusted to make the device more or less conservative/aggressive. If you haven’t read up on the subject, I suggest you leave it set at the default. Google is your friend.
The Predator I had was upgraded with the Variable Permeability Model (VPM-B). This takes into account the possible formation of micro-bubbles, so that the gradient factors can be applied only in the shallower part of a dive.
At the time of writing, VPM is the most widely used model by deep divers, and tends to demand stops at greater depths than more conventional algorithms.

The Display
The organic light-emitting diode (OLED) display provides the opportunity to add colour to the numerical information displayed. Regular stuff is in green. Things that need your immediate attention are in yellow, and if it’s urgent, it’s in red. If worse than urgent, the red figures flash.
For example, a low-battery icon is displayed in yellow. By the time it’s red you would, one hopes, have changed the battery.
A fast ascent will change the ascent-rate indicator through green, through yellow, to red and flashing red, depending on rate of ascent.
If you reach a stop-depth ceiling, it displays in red. If you ascend past the ceiling, it flashes.
All the figures are unmistakably readable. There is everything you would expect, including current depth, dive time, first deco depth and stop time. Other elements include the fraction of oxygen in the breathing gas, the average depth of the dive updated once per second, and the mode, in this case OC for open-circuit.
The current gas mix in use is displayed as O2/HE. This flashes red if you have programmed in a more appropriate gas mix for your current depth.
The no-stop time is displayed in green until there is only five minutes’ worth left, in which case it turns yellow. The depth ceiling flashes red if you exceed it.
The Predator displays the raw percentage of the Buhlmann-allowable super-saturation at the current depth and time-to-surface at 10m/min plus stops. It also displays the maximum depth achieved on that dive.
Alarms in yellow are displayed until dismissed by pressing the Select button.
Although the user has the option to choose one of three brightness settings for the display, there is also an auto setting that takes into account natural light.

Setting Up
The Predator is set up and operated using a couple of piezo-type buttons, one at each end. It is totally intuitive, and the instruction manual supplied on a CD is one of the clearest sets of step-by-step instructions I have ever come across.
You can easily set the device up with the different mixes you choose to take with you.
The popularity of its adoption as the computer of choice for many eCCR manufacturers means that a lot of the manual is devoted to closed-circuit operation, but don’t let that put you off. You can preset up to five gases in OC mode.
There is also a comprehensive dive-planning mode that will allow you to calculate decompression profiles for simple square-profile dives. The logbook has 20 hours of diving memory.
The battery is a 3.6V lithium AA unit that can be user-changed with the aid of a coin.

Firmwear Upload & Dive Log Download
The Predator uses a Bluetooth connection and comes with a dongle for plugging into a USB port on your home computer.
If you’d told me a few years ago about the advances in computer communications, I might not have believed you.

In The Water
During a dive, everything was unmistakably clear. If I wanted any information that was not immediately apparent, I could push one of the buttons and get what I wanted.
Within the confines of a wreck or in the dark, the OLED display was a delight, and yet it was bright enough and the screen glass flat enough to read in the brightly lit shallows without any annoying reflections to obscure my view.
As I mentioned at the start, my introduction to the Predator was alongside the JJ-CCR, which gave me a lot more things to concern me as I was put through the hoops.
The one thing I never had to worry about was reading and understanding what the Shearwater Predator was telling me.

Liquivision Xeo, £736
VR Technology VRX OLED, from £945

PRICE from £893
BATTERY User-changeable AA-size 3.6V lithium
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