I found that immensely satisfying.
You can set gases containing from 21% to
100% oxygen, so a bottom gas of air and a deco
gas containing a higher proportion of oxygen is
easily managed.
I used the Geo4 on a Red Sea trip, monitoring
deco status for a single back-mounted 12-litre
cylinder and then as a two-mix unit, when I
supplemented that with a second bottle clipped
as a stage and containing a richer nitrox mix.
It was easy to integrate setting the computer
with checking the gas(es) in my tanks, adding
very little to the pre-dive testing time.
In Use
In the water the data provided was very clear and
easily read. My second reservation about watch
size units is that the numbers can look weeny at
a glance, but this display was clearly legible, with
all the info you need and nothing you don’t.
Stray into mandatory deco and the display
remained equally easy to interpret and use, with
enough information to allow full control of the
dive and the stops.
And, not being gas-integrated, you also need to
be that bit more aware of what you’re doing and
the gas supply remaining, something I prefer.
Gas-switching was a simple two-button
process you can’t trigger by accident, and you can
switch to either pre-set mix, provided the gas to
which you’re switching is suitable for your current
depth, as determined by the oxygen content and
maximum allowable partial pressure you’ve set.
Switching back to your other gas is equally
easy, if required, and an icon at the bottom of the
screen tells you which gas the computer believes
you’re breathing, so that you can check that you’re
both on the same dive-plan.
Algorithms
On the subject of mandatory deco, the Geo4, like
other Oceanic computers, offers a choice of two
deco models, one more conservative than the
other. Oceanic says that the DSAT model is based
on the same data used in the PADI RDP and will
impose restrictions on repetitive deco dives, while
the Pelagic Z+ algorithm is Buhlmann ZHL-16c-
based and more conservative overall.
Some very basic tables at the back of the Geo4
manual compare the two. The manual also
divErNEt.com 71 divEr
☛
suggests that Oceanic doesn’t recommend deep
stops on decompression dives, which is where
current deco theory seems to be headed.
Once you’ve selected an algorithm and made a
dive you’re locked into using that algorithm until
24 hours after the final dive of your series, so you
can’t change your mind midway through a
liveaboard week, for example.
Not that I can see why you would. With either
option you can choose to add extra conservatism
into the settings.
For the record, I used the less-conservative
DSAT model with no additional conservatism
factored in, deep stops off and safety stops off.
I like my computers set to the bare bones of what
will get me to the surface safely, and then to addin some padding myself, typically extending the
shallower stops.
When we made three repetitive deco dives on
the Rosalie Moller, the Geo4 gave me the stops
I expected. I’ve dived that wreck a lot, so I’m pretty
much dialled into the sort of deco likely to be
required, and the Geo4 dished up no surprises.Conclusion
This is a £300 watch-style computer, which is not
a very expensive unit these days, but my only
negative was the screen.
In a world of dive computers with colourful and
permanently illuminated screens it’s a bit drab,
with black digits on a grey background, so you’ll
find you need to hit the appropriate button to
switch on the inbuilt light when light levels drop,
making the tracking of ascent rates and safety-
stop depths trickier than otherwise.
But that’s it. The Oceanic Geo4 is a fine
computer. It does everything it needs to and
nothing it doesn’t. That simplicity might or might
not appeal to you, but I really liked it and would
be very happy with one on my wrist. ■DIVER TESTS
Basic dive data for the Rosalie Mollerwreck dive from
the DiverLog+ app.Geo4 graph from the dive on Rosalie Moller. It changed
from blue to red when the dive moved into mandatory
decompression, and the blue line is a gas switch.TESTER 8 Mike Ward
PRICES 8 £320
DEPTH RATING 8 100m
CONTACT 8 oceanic.com
DIVER GUIDE★★★★★★★★★✩SPECS
MASK
ZEAGLE SCOPE
ZEAGLE IS A
US MAKERand
its origins lie
in skydiving
equipment.
Moving
into scuba, it
was a pioneer
in designing
wing-type
BCs, and an
innovator in
weight-integration.
It’s a small company,
with a website that still has
the feel of a family-run business
rather than a corporate giant.
Zeagle offers a limited selection of
products, centred on its BC line. A few regulators
and accessories make up the rest of the range.The Design
The Zeagle Scope Mono has, as you’d expect,
a single pane of glass. Zeagle also makes theScope Dual, with the two lenses that make it
easy to provide owners with off-the-rack
eyesight correction, as Zeagle does.
It can also let the mask designer set the
lenses slightly closer to your eyes, improving
peripheral vision.