The Complete Guide to Scuba Diving Computers

The Complete Guide to Scuba Diving Computers

There are many things to consider when buying a new Scuba diving computer, such as:

  • What type of diving are you doing?
  • How often do you dive?
  • What is your budget?
  • Do you do other sporting activities?
  • Do you want to wear the dive computer as a watch?

If you are new to Scuba diving, you might find yourself questioning, what is a dive computer? And do I really need one? It is really important for all Scuba divers to have their own dive computer, to track their time at depth.

In this article, I will explain why Scuba diving computers are so important, and what you need to consider when choosing the right one for you. 

What is a Scuba Dive Computer?

Scuba diving computers easily allow a diver to track their depth and dive time. They track the number of dives you have done and use built-in algorithms to calculate how long you have left on your dive, how long you should make your safety stop and how long you should leave between dives to prevent DCS. They are usually wrist-mounted like a watch.

Why do You Need a Dive Computer?

Dive computers are very important, they contain algorithms that are used to construct your no-decompression time. We need dive computers to help us dive within our limits, and reduce the risks of Decompression sickness (DCS) as built-up nitrogen is released.

No-decompression time is the time allowed to be spent at that depth, without having to make a decompression stop on your ascent.

However in most places when recreational diving, a safety stop is made at 5 meters for 3 minutes as a safety precaution. Dive computers take into consideration your depth, time, number of dives, and more.

Different computers use different algorithms, which I will go into more detail about towards the end of this article.

It is important when diving with others, to always follow the no-decompression time of the most conservative dive computer. 

Diving algorithms are used in order to avoid DCS. When following the rules, the risks of DCS are small, however, accidents do happen. The more conservative the algorithm, the smaller the risks of suffering from DCS. 

All Scuba divers should have their own diving computer, as their factors affecting the calculated no-decompression time may differ from their buddy’s. 

For example, if you have completed a dive in the morning, then go diving again in the afternoon with a new buddy who has not gone diving that day, your no-decompression time will be shorter than theirs.

This is because you have already spent time breathing air at depth, therefore you’ll have a smaller allowance on your second dive.

It is also important to remember that you always follow the computer with the shortest no-decompression time. If your computer allows you to spend 15 minutes at 25m but your dive buddy has only 10 minutes, you should only be at 25m for a maximum of 10 minutes.

hands reaching for the surface with a dive computer on left wrist

How do Scuba Diving Computers Work?

Scuba diving computers use the internal algorithm to calculate the no-decompression time. Before Scuba diving computers, dive tables were used to manually calculate the time allowed at your maximum depth.

However, these tables can be a little restricting and assume that you descend straight to your maximum depth, remain there for your given time, then ascend up. 

However, this is hardly ever the case.

In recreational diving, your dive profile is never usually in this U-shape. You may take longer to reach your maximum depth, or slowly ascend during the dive. 

These factors make it more difficult to use dive tables. Scuba diving computers can consider all of this information, and calculate the no-decompression time for you. These computers are more accurate, thus making the dive tables redundant. 

What Type of Dive Computer do you Need?

If you are a recreational scuba diver, you are likely to require a basic Scuba diving computer. However, if you are a professional or tech diver, you may require a more advanced dive computer. Different Scuba diving computers can cater to different types of diving.

A basic computer has a clear display screen, showing the time and date while on the surface. Once a dive computer is submerged, it will automatically switch to dive mode, showing your dive time, depth, and no-decompression time. 

Most basic dive computers have a couple of buttons, making it simple for beginners to navigate. They also have the ability for enriched-air mode, for example when you are using NITROX, in addition to air and freediving.

Computers made for more advanced types of diving will have a higher number of modes, such as recreational, technical, closed circuits, and gauge.

After diving, simple dive computers can run through your dive profile, show your maximum depth and add it to your dive log. More advanced diving computers can show your dive profile as a graph on the screen, and can even be connected to a computer or app on your phone to analyze the dive.

How often do you dive?

Another important thing to consider when choosing a dive computer is how often you will dive and wear the computer. If you dive very often, you might consider spending more money on an amazing dive computer which is small and comfortable to be worn frequently. 

A lot of professional divers who dive multiple times every day keep their computers on throughout the day. Therefore, a computer that is small, compact, and comfortable to be worn all day may be better for them.

Dive computers do not always have to be worn on the wrist, although this is most common. Some scuba divers have their dive computer attached to their SPG on their second stage. This is called a console computer. 

This can be a nice way to dive if you do not want a computer on your wrist, however, you will have to keep constantly checking it. Wearing a dive computer on your wrist is convenient, as it is always in your eye line. 

Smartwatches with dive computer abilities are available and may be well suited for someone who does lots of sport. Therefore investing in a dive computer that is also capable of tracking exercise might be more appropriate. 

Some computers with sport modes can have GPS, can monitor your location, heart rate, and air consumption. Such dive computers could track your run one day, then your dive the next! 

What is Your Dive Computer Budget?

It is really important to decide on a budget when considering buying a new computer. This comes hand in hand with how often you dive. 

If you only dive on holidays during the summer, you may not want to spend your life savings on the latest dive computer. A simple, recreational dive computer will be sufficient.

Although budgets are important, quite a few of the most popular dive computers are within the same price range. With the obvious exceptions of the newest, latest models and more expensive brands.

Therefore, although the price is a factor, there are many other factors that should be considered.

Where will you be diving?

You might not think about it when first buying a new dive computer, but it is important to think about where you will be diving. If you are diving in Europe, America, or Australia, finding somewhere to service your dive computer is pretty easy. 

However, if you are diving on a remote island in the tropics, it might only be possible to service the most common/popular dive computers. 

What kind of conditions you are diving in may also impact your decision on which dive computer is best suited.

Most dive computers are suitable for recreational diving, with the exception of a few being more robust for ice dives. They can withstand the colder temperatures and have adaptions for longer wrist straps to go over a dry suit. 

Technical diver wearing lots of gear

Should you Consider the Brand When Choosing a Dive Computer?

There are many different Scuba diving brands out there, which are all very capable of giving you a safe dive. Although there are numerous brands, we will be looking at the most popular.

  • Suunto
  • Shearwater 
  • Aqualung
  • Mares
  • Oceanic

Almost all scuba diving computers these days will have the option to change the colour of the straps, connect to apps, computers and have different options for air and NITROX modes. 

Generally, they only have a few buttons, making them easy to switch through the functions. 

Suunto Dive Computers

Suunto is one of the best manufactures in the world, and one of the most popular brands for dive computers for recreational divers. Most recreational divers use a Suunto dive computer for a few reasons.

Suunto uses a very safe algorithm called the Reduced gradient bubble model (RGBM). Suunto was the first to start manufacturing computers with this algorithm, and now others are following suit.

RGBM is known as ‘Bubbles’ and is one of the most conservative algorithms, which is great for beginners and recreational scuba diving.

It is based on nine tissue components and takes into consideration the small bubbles in your bloodstream which could potentially grow and cause DCS.

Another amazing thing about Suunto is that they are incredibly easy to service. You could be diving on a remote island in Indonesia and someone nearby will know where you can service or fix a Suunto dive computer.

However, although this algorithm is conservative, it can be seen as very basic. If you stay at a depth for too long, the computer will make you do a 6-minute decompression stop. Suunto is not used much for tech diving, as others may be more equipped. 

Some of the very popular Suunto models include the D4i and D5. (My own dive computer is a Suunto D4i)

Shearwater Dive Computers

Shearwater is also an amazing brand for scuba diving computers. Shearwater dive computers look very smart, are compact and comfortable. 

This brand uses an algorithm called Bühlmann. It is more commonly used for technical diving because it is designed for this type of diving. Most Technical divers have a Shearwater dive computer, as their no-decompression limits are more accurate, which is a huge benefit when diving deep and for longer. 

Shearwater dive computers are designed for technical diving, due to their very advanced, multiple modes and features.

For example, with the Teric, you can set it to freediving, recreational, technical, closed-circuit/bailout, and gauge. 

This dive computer is very beautiful, as you can customise the display and strap to suit your style. It is also very impressive due to its wireless BlueTooth connection, allowing you to download and display your dives on your computer to analyze the dive.

Other than the Teric, these dive computers are not likely to be worn all day.

They are very specifically designed for diving, and some of them are slightly bulky and impractical as an everyday watch. However technical divers favor the large screen to provide clarity and reduce confusion.

Some of the most popular Shearwater dive computers include Teric and Petrel.

Aqualung Dive Computers

Aqualung is a very impressive diving brand, also one of the best in the world. Aqualung dive computers are top of the range, along with lots of their other equipment such as fins, wetsuits, BCDs, and regulators. 

Aqualung uses an algorithm called Pelagiz Z+, which was based on the Bühlmann. It is a great algorithm for a safety-conscious recreational scuba diver.

Like all other brands, Aqualung has numerous dive computers, ranging from wrist computers to consoles connected to your first stage. 

The most popular Aqualung scuba diving computers are i300C and i40T.

Mares Dive Computers

Mares is another incredibly popular line of diving equipment, using the RGBM algorithm, the same as Suunto.

Mares computers are also very simple to use, mainly used for recreational diving.

Popular Mares computers include the Matrix, Quad, and Smart.

Oceanic Dive Computers

Oceanic dive computers also use a Dual algorithm, which allows you to switch between two to adjust your no-decompression limits according to your dive. 

Oceanic also has a good selection of console computers, which can connect to your SPG on your first stage.

Popular Oceanic dive computers include the Geo 4.0 and the Oci computer.

Don’t Forget Your Dive Insurance!

Before you go out on any dive trip or holiday, it is essential to make sure you have insurance that covers you if something goes wrong. Check out our dive insurance article for more information.

Or go straight to these dive insurance company websites:


Diver Alert Network (DAN)

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To conclude, there are many things you should consider when buying a dive computer. How often you will dive will impact how much you are willing to spend, and whether you want to wear it as a watch outside of scuba diving!

There are many dive computers to choose from, from numerous different brands. Choosing a dive computer is entirely dependent on your individual needs and tastes. 

Dive computers are intended to keep you safe and to reduce your risks of DCS, as long as you respect them and dive within your limits. 

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Bethany Nyquist

Bethany is a writer, an Environmental Scientist and Dive Master, exploring the underwater world. Practising Underwater Photography, Bethany aims to raise awareness for and help protect marine life.

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