Jun 2014

Selecting a Dive Computer

By Mike Waddington

It wasn’t too long ago when dive computers were a rare thing to see. Almost all dive planning was done using tables such as the US Navy tables or the DSAT Recreation Dive Planner. Many divers did not trust this large wrist-mounted watch that told you how long you could stay down for, and they were right not to fully trust them. They were only to be used alongside with dive tables so that if anything did go wrong the diver could easily spot them.

Nowadays dive computers are seen on the wrist of every dive professional and avid divers alike, I have even taught open water students who have come for their first confined session with their own computer. In fact, many divers choose to have a second computer as back up so if one fails they can safely ascend using the second. There are many advantages of using a dive computer, however, many divers start to switch off their brain underwater as they believe the computer will always look after them. For this reason it is always a good idea to have a good knowledge of the tables, At least know the NDL (no-decompression limit) for a few depths you will be diving, instead of getting down to 30 metres and your computer giving you an NDL of 50 minutes; it is supposed to be 20 minutes!

You will find that different computers can give slightly different readings, such as different NDL’s at certain depths. This is because they use different algorithms. This shouldn’t create too much of a problem as for safety when diving in a group you should always follow to the most conservative computer anyway.

Dive Computer features

All computers have a few features in common, they are all either wrist-mounted or gauge mounted, although Oceanic have produced a computer/mask combination which allows you to read your information through a HUD (Heads up display). All computers will read your current depth, maximum depth, current time, dive time and NDL. Most of them also include temperature and a stopwatch. They also have built-in alarms as warnings for low NDL, ascent rate warning and bottom time/maximum depth.

How to Choose a Dive Computer?

When selecting a dive computer there are many different features you will need to look, many of them require to be sent to the manufacturer to have the battery changed where some are user-changeable. Nowadays all computers come with standard air setting and nitrox settings up to 50%, but if you are thinking about Trimix diving then you can get multi gas computers as well. The market has even opened up to make them into fashionable items with most manufacturers producing wrist watch sized computers so you can wear them when not diving.

Also, a nice feature which is becoming more and more popular is air integration. These computers come with a transmitter that you attach to the high-pressure port of your regulator 1st stage (although you should still have an SPG for back up) and transmits a signal to your computer not only telling you your current tank pressure, but it also calculates how long your dive will last with your current air consumption. Not a bad feature to have!

When choosing your computer it is always a nice idea to check the features of a few models and not just go for the most basic. For instance, you can pick up a Suunto Zoop for around £170 however for an additional £50 you can pick up a Suunto Vyper which allows you to turn off your decompression information turning it into a depth gauge timer, A nice feature if you want to get into mixed-gas decompression diving. It is annoying when you have to replace a perfectly good piece of equipment because it isn’t capable of allowing you to progress in your scuba career.

Most computers usually come with computer software which is basically a logbook that also keeps track of your dive profile, and allows to track exactly where you were at each second of the dive. Some computers come with the USB cable free of charge, where others you have to buy separately, sometimes costing up to £50!

‘Selecting a Dive Computer’ was written by Mike

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Mike Waddington

I first discovered diving in 2008 after going snorkeling on the Great Barrier Reef in Australia. After trying diving at a flooded quarry in England I decided to head out to warmer more interesting waters in Thailand where I ended on the Island of Koh Tao completing my Open Water course. Instantly addicted with money to spend and plenty of time on my hands I decided to continue until I became a Divemaster so I could live what seemed as the perfect life.

After that I headed to the Caribbean to an island called Utila to complete my instructor course, I spent several months out there completing the MSDT internship, teaching students and leading dives. This is also where I discovered my interest in the technical side of diving, taking part in equipment repair courses and learning about blending gasses and running compressors.

With all my new qualifications it was time to head back to where it had all started, Back to Koh Tao where I intended on living the dream. Once I arrived I quickly found a job and started teaching straight away. During my time on Koh Tao I took part in all many technical diving courses, learning how to dive with re-breathers, in caves and even going down to 90m/300ft!


PADI Master Scuba Diver Trainer
PADI/DSAT Tech Deep Instructor
PADI/DSAT Gas Trimix Gas Blender
PADI/DSAT Trimix Diver
TDI Intro to Cave Diver
TDI Advanced Wreck Diver
TDI Inspiration rebreather Decompression Procedures
PADI Professional Videographer
BSAC Compressor Operator
TDI Equipment Service Technician

Dream Dive Locations:

Silfra, Iceland
Cenotes, Mexico
Chuuk Lagoon, Micronesia
Ice Diving in Russia