Whether you’re on an exotic diving holiday or exploring your local lake, there's some scuba diving technology that you should always have on your wrist: A dive computer. Every dive-master or scuba instructor will carry a dive computer, and if you’re planning on leading your own dives, they’re an essential bit of kit that at least one person in your party should possess.

A dive computer comes in handy when you are diving the unknown - Flickr / Travis S.

From monitoring your ascent-rate to calculating how much bottom time you have left, these clever devices also store an important historical record of your dives, which can be charted and analysed in the case of accidents, or just for interest.

With a vast range of styles and prices on the market, the level of technology required and how much you want to spend is down to personal preference.

So here's some information to help you buy:

Whilst simple, wrist computers or second-hand equipment are perfectly adequate, nitrox-compatible and wireless devices offer features that will be important for technical divers.

Wrist computers look a bit like large watches, and are probably the most popular type. Easy to transport, they’re perhaps the best to take on scuba diving holidays the world over as they double-up as everyday watches. The most obvious disadvantages are that the face of these compact dive computers can sometimes be a little too small to read easily underwater and they tend not to include a pressure gauge.

Console Dive Computers, on the other hand, feature larger readouts, which are easier to read underwater. These attach easily to your equipment, can also be clipped onto a BCD and usually include a pressure gauge.

Galileo Sol from Scubapro with an extra large dot matrix display.

Nitrox diving requires a specific - and more expensive - type of computer so, if you dive with nitrox, or are considering doing so in the future, it’s worth investing in a specialist nitrox-compatible computer, rather than wasting your money on two separate machines.

Costing more than standard models, air integrated dive computers replace the need for a submersible pressure gauge, by calculating how much bottom-time you have left at your current rate of air consumption, and allowing you to adapt your underwater behaviour to lengthen your dive.

With more cash to splash, hoseless dive computers offer another level of technology and help to streamline your kit, by transmitting wireless information between your regulator, first stage and the receiver - top of the range devices even let you check up on your buddy’s air consumption.

Memory capacity should also be a consideration when buying a dive computer. This varies considerably between different models – older dive computers may just store the most recent dive, whilst modern versions can hold 50 or more dive histories.

Suunto D4i Blue and its three dive modes: Air, Nitrox, Freedive.

The latest computers also allow you to download your dive information onto your laptop or PC, allowing you to graph and analyse your dive, or chart information such as rate violations, tank pressure and ascent rate.

Batteries are another important aspect of a dive computer. If you are going on longer scuba diving holidays then battery-life, ease of use and availability should all be considered, as well as whether battery changes can be carried out by yourself, or need to be performed at a service centre.

In terms of price, dive computers can range from less than £100 for a simple model, to well over £1000 - if you want one with the all the latest scuba diving technology and technical wizardry. It’s also possible to rent computers from dive shops, usually for around £10 a day.

Whatever style and capabilities you go for, the most important thing is that you’re able to operate your dive computer – there’s no point in taking the latest technology on your trip to the Great Barrier Reef or on a once in a lifetime diving holiday, if you don’t know how it works! Any new computer should come with a user manual that you can get to grips with at home, and most good dive shops should be able to take you through the basic functions of your computer, as part of the service.