DIVE-COMPUTERS EVOLVED quickly into “must-have” instruments. No longer are divers restricted to using table calculations for flat-profile diving; by consulting your on-board digital display you know your exact depth, how long you’ve been there and, more importantly, how long you can stay there without saturating your body tissues with inert gases.
The days of complicated calculations to prepare gas requirements, run-times, bail-outs and decompression penalties for mixed-gas technical diving are also over. Modern dive-computers can assimilate all the information needed in real time and in real-world conditions.
We’ve put together a group overview of a selection of current computer models as a guide when deciding on which model best suits your preferences, style, type of diving, experience and, of course, budget.
Conducting a full underwater comparison test as DIVER used to do makes little sense in the modern world, because instead of set algorithms to compare, today’s units offer user-defined individual settings.

ALGORITHMS
Decompression algorithms are advanced dive-tables used in conjunction with a depth-sensor and timer. Researchers have for years experimented with these complicated formulae, calculating the levels of various gases in a diver’s blood and tissues and working out how they act in their bodies.
Their biggest challenge has been to find an all-encompassing formula that will keep everyone safe regardless of age, body size, shape, fat content, gender or fitness level. We’re all different and we all absorb and release gases at different rates during a dive.
The ideal solution would be to stick a needle in an arm and link it to some form of superbiological computer that can work out exactly what’s micro-bubbling away in our bodies. This holy grail for bio-boffins remains some way off, so we rely on more generalised calculations.
Most computers now have a way of taking into account your personal levels of conservatism. These can be changed from day to day or even dive to dive, to take into account factors such as changed underwater conditions, ambient temperature, fitness or fatigue.
By adjusting these settings, your instrument will either lengthen or shorten no-stop times to become more or less conservative.
Some models provide a choice of algorithms, as well as the option to include or exclude deep stops in the decompression calculations.

MIXED GASES, OPEN- OR CLOSED-CIRCUIT?
Nitrox has become a popular choice of breathing gas for recreational divers, and in some parts of the world it’s easier to obtain than plain old compressed air. Some resorts offer it free to suitably qualified divers.
The calculations required to plan a dive using nitrox are simple enough, but when it comes to gas-switching during the dive to minimise decompression penalties, or full-on technical diving with helium in the mix, the calculations become a lot more intricate.
This is the domain of technical dive-computers, electronic tools that calculate not only the ideal mix of gases for the planned dive but also bail-out and deco gas requirements, relaying this critical information in real time during the dive phase.
They allow the user to pre-input various mixes that are then accessible during the dive. Some models are loaded with programs that can calculate safe dive-profiles when using fixed-partial-pressure oxygen closed-circuit rebreathers. However, the CCR’s own dedicated computer, linked directly to the unit’s O2 cells, is generally seen as a better option, with the standalone computers usually employed as back-up.

DISPLAYS
It’s no good having all that risk-critical information to hand if you can’t read it, and some of the biggest advances in display technology have been incorporated into dive-computers’ evolution.
In the past, monochrome liquid crystal was the only choice, and remains the most commonly used. There are two types of monochrome graphic LCD displays. One uses segments strategically placed to form numbers and letters (similar to a standard calculator); the other, with a matrix of liquid-crystal dots set over the whole display, can create symbols and graphics as well as numbers and letters over a wider area. Both types of screen can be lit from behind to suit low-light conditions.
A more up-to-date display using technology found in modern TV screens is the organic light-emitting diode or OLED.
The digits themselves light up to give a brighter, clearer view, and can also be illuminated in different colours to be more distinguishable, helping the viewer to assimilate critical information.
Because the digits themselves are lit there’s little need for backlighting, even in low-light conditions.
The latest screen technology is a derivative of what we see in smartphones and tablets – full-colour LCD TFT.
This uses the light-moulding properties of liquid crystals to display clear, crisp images and colours directly onto the screen.
The liquid crystals don’t emit light directly and need to be permanently backlit. Full-colour LCDs are currently the most popular colour displays in use.

SCREENS
Displays need to be set behind a screen to avoid water contact and damage, and these can be made from polymers such as acrylic or Plexiglas, or from toughened glass, sometimes referred to as sapphire-crystal which, unlike polymer screens, is scratch-resistant.
An air-gap between screen and display causes refraction, so the screen becomes mirrored when viewed from an acute angle, but displays that are bonded to the screen can be viewed from very tight angles.

DISPLAYED INFORMATION
Critical data such as current depth, dive-time, no-deco limits and deco ceilings need to be prominent to allow the user to quickly assimilate and instantly act on it. This can be achieved using bold characters, larger fonts or differing colours (depending on the type of display).
Non-essential or nice-to-know information such as date, current time or water temperature doesn’t need to be as prominent or, on smaller displays, shown at all.
Displays can be customised or personalised to provide a layout to suit the user’s needs. Most have language options and some have selectable graphic and icon options. OLED and full-colour LCD displays often feature customisable colour options, making risk-critical information instantly recognisable.

MODES & FUNCTIONS
Among the functions found on all but a few computers are Freedive and Gauge modes, which bypass the algorithm in favour of displaying only current depth, maximum depth and immersion time.
These are useful when using the computer as a bottom-timer in tandem with tables for fixed-run-time mixed-gas diving, or as a gauging tool for breath-hold diving.
Among other functions now incorporated into most models is a digital compass, which can invariably be accessed with a single button-push and displayed in various formats to aid underwater navigation.
Common to most dive-computers are date, time, alarm-clock and stopwatch functions, especially on models designed to be worn every day watch-style – but fewer models offer functions such as a barometer, moon-phase indicator, pedometer, magnetometer, altimeter or pitch-and-roll indicator.

POWER
Dive-computers run on electricity from an array of power sources, and fortunately we’re seeing leaps in battery technology cascading down.
Some units use disposable alkaline batteries, others rechargeable lithium-ion cells that can be service-technician- or user-replaceable, factory-sealed and rechargeable while in situ, or even charged through induction.
Various charging methods include mains-socket chargers and USB leads from phone and tablet chargers or directly from desktop computers. One model even employs a USB-supplied induction plate to avoid any physical connections.

CONTROLS & DATA TRANSFER
All models need a way for the diver to access the menus, adjust the settings, download dive-data in the form of logbook entries and upload firmware upgrades.
Most models employ push-buttons to access on-board menus and functions, and the buttons can be spring-loaded and O-ring-sealed, sealed piezo-electric or magnetic.
The number of buttons can range from one to four, and one model has no buttons at all – it’s accessed using taps to the body.
Data-transfer and firmware upgrades can be achieved using model-specific cradles and cables, USB charging ports or Bluetooth technology.

GAS INTEGRATION
Some computers are linked directly to the scuba unit’s first-stage high-pressure port via a direct-feed hose. Others use electronic transmitters, again connected directly to a regulator hp port, and these instruments display real-time tank pressures digitally, with some calculating remaining dive-time based on actual gas consumption.
A number of technical models allow for more than one electronic transmitter to be connected when using multiple tank configurations. One unit can read and display up to 10 other divers’ tank pressures – ideal for instructors keeping an eye on their students.

MOUNTING OPTIONS
To be effective, a computer needs to be placed in a prominent, easily accessible position. Most are suitable for wrist- or lower-forearm-mounting, with watch-style buckle-straps the most popular.
Some use elasticated webbing and trident clips for forearm mounting and some technical models use fixed twin-bungee cords.
It’s all about security and stability, because if a computer is lost through strap failure on a dive, the outcome could be dangerous. A loose-fitting strap or one that doesn’t adjust to compensate for suit compression can lead to the computer flopping around or falling off.
The back-surface profile of larger block-style computers helps with stability, with most conforming to the natural contours of the arm.
A convex inner profile reduces the contact surface area and is possibly the least stable.
A few forward-thinking exposure-suit makers have taken all this into account and provide computer-strap keeper bands to address this all-too-common problem.
Some underwater photographers like to mount their computers on their camera-arm systems so that they can see the display without moving their eyes too far from their viewfinders.
High-pressure-hose-linked gas-integration models are usually attached to a suitable BC D-ring via a piston-clip or retractable lanyard to form an easily accessible console.

ACCESSORIES
There aren’t that many dive-computer accessories around, other than security lanyards, strap-extensions for drysuit-diving and screen-protectors. One European maker offers a dedicated oxygen analyser for its instruments, but the resulting gas mix still needs to be entered into its computers manually to avoid any litigation issues.
A few models go a step further by integrating a wireless polar-style chest-band to monitor and record the diver’s heart rate and skin temperature during the dive, and constantly re-adjust the resulting deco calculations based on real-time, real-person data.

GLIMPSE OF THE FUTURE
They say 2.6 billion people owned a smartphone in 2014, and this is predicted to rise to 6.1 billion by 2020 – that’s 70% of the planet’s human population. It follows, then, that these advanced media devices will be considered as suitable for use as dive computers.
In fact this evolution has already begun, with German company Scuba Capsule producing an app and depth-rated smart case that converts your iPhone into a full-blown mixed-gas computer that has the ability to record videos and take stills at the same time.


CONTACTS:
Aqua Lung www.aqualung.com/uk
Atomic www.atomicaquatics.com
Cressi www.cressi.co.uk
HW www.deep-ideas.co.uk
Liquivision www.liquivision.com
Mares www.mares.com
Ratio www.liquidsports.co.uk
Scuba Capsule www.scubacapsule.com www.blue-orb.uk
Scubapro www.scubapro.com
Shearwater www.narkedat90.com
Suunto www.suunto.com
TUSA www.tusa.com


Suunto Zoop Novo £189
This large wrist-mounted unit for recreational diving can be used with a single gas (air or nitrox) and features full decompression capabilities. It is compatible with Suunto DM5 software for PC and Mac.
Algorithm: Suunto RGBM
Gas Options: Air or nitrox
Closed Circuit: No
Display: Dot-matrix LCD with backlight
Modes: Air, Nitrox, Gauge, Freedive, Off
Battery: User-replaceable li-ion CR2450
Access: 4 buttons
Data Transfer: USB cable
Gas Integration: No
Mounting: Elastomer strap with buckle
Accessories: Display shield, data-transfer cable


Mares Puck Air Integrated £277
Console-mounted air-integrated computer for recreational diving. The display shows real-time tank pressure, time to reserve and gas consumption.
Algorithm: RGBM Mares-Wienke (10 tissues)
Gas Options: Air or nitrox (21-50%)
Closed Circuit: No
Display: Combined segmented and dot-matrix LCD with backlight
Modes: Air, Nitrox, Bottom-time.
Battery: User-replaceable CR2450 li-ion
Access: 1 button
Data Transfer: DRAK USB (optional)
Gas Integration: High-pressure hose
Mounting: Piston-clip or lanyard (not supplied)
Accessories: Analogue compass (+ £44)


TUSA Talis £290
This watch-style, recreational air or two-nitrox-mix computer with automatic altitude adjustment comes in black, pink, white and blue or twin-colour combinations of each.
Algorithm: TUSA Bühlmann ZHL-16C
Gas Options: 2 switchable nitrox mixes (21-50% & 21-99%)
Closed Circuit: No
Display: Segmented LCD with backlight
Modes: Air, Nitrox, Gauge, Freedive, Watch
Battery: User-replaceable CR2430 li-ion
Access: 4 buttons
Data Transfer: PC interface
Gas Integration: No
Mounting: Watch strap & buckle
Accessories: PC interface


Mares Matrix £328
This watch-style computer with stainless-steel body and synthetic strap features a tilt-compensating digital compass and is software upgradeable from PC or Mac via the charging cradle and USB lead.
Algorithm: RGBM Mares-Wienke (10 tissues)
Gas Options: 3 switchable nitrox mixes (21-99%)
Closed Circuit: No
Display: Dot-matrix LCD with backlight
Modes: Air, Nitrox, Planner, Watch, Calendar
Battery: Rechargeable, factory-sealed li-ion
Access: 4 buttons
Data Transfer: Charging cradle USB cable
Gas Integration: No
Mounting: Watch strap & buckle
Accessories: Screen protector, metal strap, tech strap


Ratio iDive Easy £375
This Italian computer comes in eight colours, and additional features include a 3D tilt-compensating compass. It has pre-loaded apps including moon-phase calendar, barometer, magnetometer and altimeter plus a pitch-and-roll function.
Algorithm: Buhlmann ZHL-16B
Gas Options: Gas-switching, 2 gases, air, nitrox
Closed Circuit: No
Display: Dot-matrix LCD with backlight
Modes: Air, Nitrox, Freedive, Gauge
Battery: Factory-sealed, USB-rechargeable li-ion
Access: 4 buttons
Data Transfer: USB cable
Gas Integration: No
Mounting: Silicon strap with buckle
Accessories: Ratio O2 analyser (£200)


Cressi Newton £379
This recreational watch-style model with 48mm display can be worn as an everyday timepiece and is PC- and Mac-compatible with the optional interface hardware. It is available with grey, pink, yellow or blue accents.
Algorithm: Cressi dual-mixture Haldane RGBM
Gas Options: 2 gases (21-99%), switchable
Closed Circuit: No
Display: Dot-matrix LCD with backlight
Modes: Air, Nitrox, Freedive, Gauge
Battery: User-changeable CR2430 li-ion
Access: 4 buttons
Data Transfer: Cressi interface hardware, USB cable
Gas Integration: No
Mounting: Rubberised ABS strap & stainless buckle
Accessories: Interface


Mares Icon HD4 Black Edition £400
An air-integrated block-style air or nitrox computer designed for recreational diving. The computer displays tank pressure, time remaining and current gas consumption as real time data and is PC- and Mac-compatible using the USB charging cable.
Algorithm: RGBM Mares-Wienke (10 tissues)
Gas Options: 3 switchable nitrox mixes (21-99%)
Closed Circuit: No
Display: Customisable full-colour LCD
Modes: Air, Nitrox, Planner, Watch, Calendar
Battery: USB-rechargeable, factory-sealed li-ion
Access: 4 buttons
Data Transfer: USB cable bi-directional communication
Gas Integration: Yes
Mounting: Wide-band rubber strap & buckle
Accessories: Wireless transmitter (£110)


HW OSTC Sport Colour £410
This recreational model has a 4Mb flash memory to store 1000hr of dive data, and encapsulated electronics – it also features a 3D tilt-compensated compass. It comes in gold, green, orange, blue, violet or silver – all colours but silver +£35.
Algorithm: Buhlmann ZHL-16C with optional gradient factors (ZHL-16C GF)
Gas Options: 3 nitrox mixes (21-100%)
Closed Circuit: No
Display: Full-colour LCD IPS-TFT
Modes: Air, Nitrox, Apnea, Gauge
Battery: User-replaceable AA cell (1.5 or 3.6V)
Access: 2 buttons
Data Transfer: Bluetooth
Gas Integration: No
Mounting: Bungee cord


Aqualung i450T £522
Wristwatch-style air-integrated recreational model featuring a high-visibility LED alarm warning light and a digital compass with North reference, return-bearing lock and declination adjustment. It comes in black/blue, all-white or black/grey with PVD finish.
Algorithm: Pelagic Z+ based on Bühlmann ZHL-16C
Gas Options: Manages up to 3 nitrox mixes (with 3 transmitters)
Closed Circuit: No
Display: Combined segmented/dot-matrix LCD with backlight
Modes: Air, Nitrox, Gauge, Freedive
Battery: User-replaceable li-ion
Access: 4 buttons
Data Transfer: PC interface
Gas Integration: With transmitter
Mounting: Watch-strap & buckle
Accessories: DiverLog software, wireless transmitter (£204)


Scubapro Mantis M2 £539
Stainless-steel-bodied watch-style model incorporating Scubapro’s “Human Factor Diving” software, which uses biometrics data from the diver’s heart rate and skin temperature for real-time, real-person deco calculations. There is also a full-tilt 3D digital compass. The unit is PC/Mac-compatible using logTRAK.
Algorithm: Predictive Multi-Gas ZHL8 ADT MB
Gas Options: 3 nitrox mixes (21-100%)
Closed Circuit: Fixed-point CCR
Display: Segmented LCD with backlight
Modes: Scuba, CCR, Freedive, Gauge
Battery: Dealer-replaceable CR2450 li-ion
Access: 4 buttons
Data Transfer: Cradle & USB cable
Gas Integration: Multi transmitters
Mounting: Watch-strap & buckle
Accessories: Scubapro HRM/body-temperature belt, wireless transmitter (+ £260 for both)


HWOSTC 2 £575
Designed by Heinrichs Weikamp, this is a completely sealed unit using wireless technology for both charging and data transfer. The battery uses Qi inductive charging through a USB-linked charging pad. The unit has a 4Mb flash memory to store 1000hr of dive data, and a 3D tilt-compensated compass.
Algorithm: Buhlmann ZHL-16C with optional gradient factors (ZHL-16C GF)
Gas Options: 6 programmable gases (nitrox, trimix or heliox)
Closed Circuit: No
Display: Full-colour LCD IPS-TFT
Modes: Air, Nitrox, OC Trimix, OC Bailout, Constant PO2 Deco, Gauge
Battery: Induction-charged factory-sealed
Access: 2 piezo-electric buttons
Data Transfer: Bluetooth
Gas Integration: No
Mounting: Bungee cord
Accessories: Supplied EVA case


Suunto D6i Novo Stealth £595
This steel-bodied watch-style instrument with sapphire-crystal glass screen has four colour schemes, a digital 3D tilt-compensating compass and is compatible with Suunto DM5 software for PC and Mac.
Algorithm: Suunto RGBM
Gas Options: Gas-switching 3 gases, air, nitrox
Closed Circuit: No
Display: Dot-matrix LCD with backlight
Modes: Air, Nitrox, Gauge, Freedive, Off
Battery: Dealer-replaceable CR2450 li-ion
Access: 4 buttons
Data Transfer: Cradle, USB cable
Gas Integration: Wireless transmitter
Mounting: Silicon strap & buckle
Accessories: Wireless transmitter (£199)


Scubapro Galileo Sol £599
Composite-bodied, oil-filled block-style unit that comes with heart-rate monitor belt. A trimix algorithm can be downloaded from scubapro.com. Full-tilt 3D digital compass and PC/Mac- compatible.
Algorithm: Predictive multi-gas ZHL8 ADT MB
Gas Options: 3 nitrox mixes (21-100%)
Closed Circuit: No
Display: Dot-matrix LCD with backlight
Modes: Scuba, Freedive, Gauge
Battery: User-replaceable CR12600SE
Access: 3 buttons
Data Transfer: Infra-red
Gas Integration: Multiple transmitters
Mounting: Wide-band rubber strap & buckle
Accessories: HRM belt. Wireless transmitter (+ £150)


Shearwater Perdix £647
A single AA alkaline battery can power this technical-diving block-style computer, though the maker recommends 3.6V SAFT LS14500 batteries. It comes with Shearwater desktop software for PC and Mac and is third-party dive-log software compatible.
Algorithm: Buhlmann ZHL-16C with gradient factors, optional VPM-B
Gas Options: Open-circuit 5 gases, closed-circuit 5 gases
Closed Circuit: Yes
Display: Full colour LCD
Modes: Air, Nitrox, OC Trimix, CC Trimix, OC Bail-out
Battery: User-replaceable AA
Access: 2 buttons
Data Transfer: Bluetooth
Gas Integration: No
Mounting: Elastic strap & buckle. Bungee. Latex surgical tubing
Accessories: Screen protector. VPM-B upgrade (£54)


Suunto Eon Steel £749
Block-style model in composite materials with stainless-steel bezel and customisable TFT LED colour display bonded to Xensation toughened glass screen. It has a tilt-compensating 3D digital compass, rubberised body protector and is compatible with Suunto DM5 PC/Mac software.
Algorithm: Suunto Fused RGBM
Gas Options: Gas-switching, 10 gases. Air, trimix, nitrox
Closed Circuit: Fixed-point CCR
Display: Customisable full-colour TFT, backlit LED
Modes: Gauge, Air, Nitrox, Trimix, Fixed-Point CCR
Battery: Factory sealed rechargeable li-ion
Access: 3 buttons
Data Transfer: USB cable
Gas Integration: Wireless transmitter, multiple tank
Mounting: Elastomer strap & buckle. Bungee cord
Accessories: Suunto Tank POD (£225). Wireless transmitter


Scuba Capsule 6 £749 (ex iPhone)
This is a high-grade aluminium housing for Apple iPhone 6 and 6S smartphones. The downloadable app supports many functions and modes including digital compass, gas-mix calculator, maps and GPS. iPhone camera functions can be accessed on the dive, with the dive data shown as a heads-up display.
Algorithm: Bulmann ZHL-16C with gradient factors
Gas Options: Air, nitrox, trimix
Closed Circuit: No
Display: Full-colour LCD
Modes: Air, Nitrox, Trimix. Heads Up Display in Camera mode
Battery: Smartphone
Access: Touchscreen
Data Transfer: Bluetooth
Gas Integration: Supports Suunto transmitters
Mounting: Quarter-inch tripod screw, strap-mounting options.
Accessories: Downloadable apps


Atomic Aquatics Cobalt 2 £857
This hp hose gas-integrated computer is fitted with a quick-disconnect hose attachment as standard. It uses watertight magnetic buttons to access menus and functions, has a 3D tilt-compensating digital compass, and can be connected to PCs or Macs.
Algorithm: Recreational RGBM Mares-Wienke (15 compartments)
Gas Options: Up to 6 user-defined air or nitrox (21-99%) mixes
Closed Circuit: No
Display: Full-colour LCD
Modes: Air, Nitrox
Battery: Built-in rechargeable li-ion
Access: 4 buttons
Data Transfer: USB cable
Gas Integration: High-pressure hose
Mounting: Piston clip or lanyard (not supplied)
Accessories: Ballistic nylon case. Optional coloured top covers (£20)


Ratio iX3M Tech+ £999
This model has extra features including a 3D tilt-compensating compass, surface GPS, acoustic and vibration alarms. It comes with loaded apps including moon-phase calendar, barometer, magnetometer and altimeter plus pitch-and-roll function.
Algorithm: User-selectable Buhlmann ZHL-16B or VPM-B
Gas Options: 10 settable gas mixes
Closed Circuit: Fixed-point CCR
Display: Customisable full-colour LCD
Modes: Air, Nitrox, Trimix, CCR, Freedive, Gauge
Battery: Integrated USB-rechargeable li-ion
Access: 4 buttons
Data Transfer: USB cable
Gas Integration: No
Mounting: Twin elastic webbing & trident-clip
Accessories: Ratio O2 analyser (£200)


Liquivision Lynx Air Integrated £1185
Said to be the only dive-computer that combines wireless connectivity with intuitive “Tap Navigation”, the most expensive model in this round-up comes with the U-2 tank transmitter, allowing gas- monitoring of the wearer and also of the gas supplies and location of up to 10 other divers within 100m. It’s also compatible with the L1 location transmitter, which can mark the position of dive-boats or underwater landmarks, and features a digital compass.
Algorithm: Unspecified
Gas Options: 3, Air, Nitrox (21-100%)
Closed Circuit: No
Display: OLED full colour
Modes: Logbook, Planner, Simulator
Battery: Disposable
Access: Tap Navigation
Data Transfer: PC / Mac interface
Gas Integration: Via U-2 transmitter
Mounting: Rubber strap. Bungee cord.
Accessories: L1 Ultrasonic transmitters

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