Computers
Purpose
Dive computers have become an essential part of your scuba diving gear. A dive computer will provide valuable information before, during, and after each dive. Before your dive, the computer will help you with depth and bottom time planning. During the dive, you can see important data such as current depth, maximum depth, dive time, no-deco lmit, deco time, ascent rate, water temperature. After the dive, you will have access to the dive log to show you all the detail of your dive.
A dive computer is far more precise than dive tables, which calculate based on the maximum depth of the dive rather than your actual depth profile. A dive computer lets you stay at depth longer and more safely by giving you up-to-date information at every moment.
Features
Style
Dive computers can be either part of your console along with a pressure gauge (and compass) or it can be worn on your wrist. Wrist style computers can also be worn while snorkeling and free diving. In terms of size, a wrist style can be a smaller, watch-size or a larger, hockey-puck size. Another type of computer is a HUD (heads-up display) that is attached to or near your dive mask and provides information about your dive right in your line of sight.
Air Integration
Some dive computers will allow you to integrate the air pressure reading from your scuba tank. In a console style, the computer will usually replace your depth and pressure gauges. In a wrist style, you will need a transmitter that fits into the first stage of your regulator, usually you will still have a backup set of analog gauges in a console as well. Air-integration will allow the computer to calculate your remaining surface air consumption (SAC) rate, display current tank pressure, and factor your air supply into NDL calculations — telling you not just how long the decompression algorithm allows you to stay, but how long your air will actually last. Air integration is one of the most useful features available on modern dive computers. It replaces the need for a separate SPG, though many divers keep an SPG as a backup.
Nitrox Compatible
Most modern dive computers support enriched air nitrox (EAN), allowing you to input your oxygen percentage so the computer can adjust NDL calculations accordingly. Even if you primarily dive air, nitrox capability is worth having as you expand your diving.
Downloadable
Many current computers connect via Bluetooth to smartphone apps for automatic dive logging, gas planning, and firmware updates. This eliminates the need for a separate dive log book and makes tracking your dive history effortless.
Alarms
These may be visual or audible and will usually indicate warnings such as ascent rate, exceeding NDL, exceeding max depth, etc. Some dive computers may also vibrate to indicate an alarm.
Algorithm
All dive computers use a decompression algorithm (commonly Bühlmann, RGBM, or a proprietary variant) to calculate no-decompression limits. Most allow you to adjust the conservatism level — increasing conservatism adds safety margin, which is useful for divers making multiple dives per day, older divers, or anyone who runs cold. Dialing it back slightly can extend bottom time for experienced divers who run warm and dive conservatively by nature.
Modes
All computers will have a Dive mode which give you information during the dive including depth, bottom time, and your no-decompression limit. The Log mode is used on the surface and will give you the information from past dives, including max depth, average depth, actual bottom time, water temperature just to name a few. The Plan mode will be useful prior to the dive as it will indicate a variety of depths and the no-decompression limit at that depth, based on your immediate dive history, to help plan your next dive. Other modes that may be available depending on the computer model include Gauge mode, which allows you to run the computer as a bottom timer and depth indicator only, and Freedive mode, which allows you to record your freediving/snorkeling activities.
Other Funcutions and Features
These will vary from computer to computer and are worth a detailed look. Every diver has different needs and preferences you should look for what appeals to you and your diving style. User changable battery, digital compass and multiple gas mix are a few examples.
Care & Maintenance
Rinse your dive computer with fresh water after every dive and dry completely before charging or changing batteries. Better yet, give it a good soak in some warm, fresh water. Inspect the battery compartment oring annually and replace as recommended by the manufacturer — a failed battery oring is one of the most common causes of computer flooding. Keep the display protected with a screen protector if available. Have the computer checked by a service technician if it behaves unusually or if any buttons or seals show wear.