Best Backup Dive Computer – Never Dive Without One

On a dive trip years ago, my trusty Perdix died on me. On another, the replacement battery failed. Thankfully, these incidents happened near the end of my trip. I had considered what would have happened if they failed at the start, and concluded that I would have wasted two precious days of diving. Now, I don’t dive without a backup.

These are just some of the reasons why having a backup dive computer is so important. In this article, we will discuss the benefits of having a backup dive computer, provide our recommendations of the best ones, and go over the criteria we used to make our list.

Our Top Picks:

Risks of Diving Without a Backup

If your main dive computer suddenly fails, you have to deal with a whole host of issues. When diving daily, a dive computer barely clears to a de-saturated level when left overnight. Also, each dive you make should be measured as part of a series so that a dive computer can create the most accurate dive profile.

Any break in this crucial process, and your replacement dive computer will not have the most accurate information to monitor or plan for subsequent dives. As such, even though getting a replacement via renting is possible, it’s not recommended because the fresh dive profile will be inaccurate.

Furthermore, when there is such a gap in the available data, the standard procedure is simply to surface and wait 24-48 hours before diving with a replacement computer. If you have easy access to the dive site, it’s not a problem. If you’re on holiday, each day is costing you a lot of money. With a backup dive computer, if anything happens to the main one, simply swap over to the spare and continue diving as usual..

Do You Need a Backup Dive Computer?

If you want to be prepared for the worst, then you should bring spares of anything critical. That means extra O-rings, mask and fin straps, wire straps for attaching gear, dive computer batteries, or even a spare backup computer. Put all of these key items in a small box, and you can be set to handle almost any unexpected equipment failures.

Having these items on hand can be the difference between calling off a dive that you planned and packed for, or allow you to continue diving using your backups. As advanced as dive computers are, sometimes they just fail. You may one day find that your expensive dive computer has turned off, possibly never to turn on again. This can happen in the middle of the dive or between dives.

Standard safety procedures are that you should surface immediately and take a day or two off from diving. If you live by the dive site, this isn’t an issue. But when you’re on holiday or a liveaboard, this is an expensive price to pay for a busted piece of hardware.

Loss of dive time isn’t even the biggest issue. Remember that a dive computer’s primary purpose, if nothing else, is to keep you from getting bent. If you end up diving deeper than originally planned, diving more frequently, or surface despite being in the computer’s “caution” zone, you are flirting with DCS. On top of that, if you’re overweight, out of shape, or elderly, you are even more susceptible.

That’s why you should have some kind of a backup device so that you have an extra margin of safety and can continue safely diving if your primary dive computer suddenly fails. It doesn’t even have to be a dive computer; any device that can be used as a bottom timer and a depth gauge are enough of a substitute for a backup dive computer.

Best Backup Dive Computers

Cressi Leonardo

The Cressi Leonardo is one of the most affordable dive computers with a simple design, making it a great choice for a backup dive computer. It is easy to navigate the interface with its large, informative display while maintaining a sleek profile that is travel-friendly. It stows nicely into your BC pocket and can be worn as a wrist watch.

For simplicity, the Cressi Leonardo only has a single button located at the bottom of the device. With just this one button, you can toggle through the menus and hold down to make a selection. Since there is only the single button, you won’t even run into the issue of forgetting which button does what. Furthermore, the interface is simplified so that it can be easily navigated with one button.

Despite being compact, the Cressi Leonardo has a large display that lets you see all of the important information at once. You can check the time, depth, decompression status, dive mode, surface intervals, battery indicator, and ascent rate at a glance. The display is high-definition, with an edge-to-edge LCD and sharp lines for legibility. You can easily monitor your vitals with this display. Our only complaint is that the backlight could be brighter.

As for dive modes, the Leonardo has: air, gauge, and nitrox modes. The air dive mode (21% oxygen, 79% nitrogen) is water-activated, so you don’t have to worry about fumbling with your backup to get it started. You can also set it in gauge mode so it acts as a bottom timer. Nitrox mode lets you dive with up to 50% oxygen.

All in all, this is a great, affordable choice for a backup dive computer. It has only the features that you need and no more. This helps keep the price low for beginners to use as a starter dive computer, and of course it can also be used as a backup device.

You can check our full review of the Cressi Leonardo by clicking here.

Oceanic B.U.D.

While any of the dive computers listed in this review can work well as a backup, the B.U.D. from Oceanic is specifically designed to be a backup device. Rather than relegating your old dive computer to the role of a backup spending $1,000 on a high-end one, perhaps you can get a few more years out of it as your primary by using the B.U.D. as your backup.

What exactly makes this so good as a backup? To start, it doesn’t have a strap to reduce bulk, and it comes with a built-in clip so you can attach it wherever you have a D-ring. It’s so small that it stows easily in your BC pocket as well. And of course, it has the basic features that you want, including dual algorithms and nitrox up to 50% oxygen.

To simplify its operation, the B.U.D. has a one-button operation to navigate its menus. The two algorithms you can switch between are Pelagic Z+ and DSAT. You can also switch between air and nitrox dive modes.

One thing we love about the B.U.D. is its battery “hot swap” feature. It will retain its current data for a window of 8 seconds while the battery is being replaced. Other dive computers will simply wipe your dive data clean upon battery removal if you haven’t backed them up. When you’re in the middle of a vacation, this simply is not feasible so a hot swap feature is appreciated.

Mares Puck Pro

The Mares Puck Pro is yet another affordable dive computer with a simplistic one button design similar to the Cressi Leonardo. You honestly can’t go wrong with either one. Both the Mares Puck Pro and the Cressi Leonardo have durable designs that can endure rough environments. Their prices are comparable, and so are their features.

The large display and one button navigation drastically simplifies its operation. Within a few minutes of playing with it, anybody can intuitively understand how it works. The Puck Pro has three modes: air, nitrox, and gauge. The gauge mode is called “bottom timer” on this model. Its batteries are user-replaceable so you can replace it before your next trip to ensure it won’t fail on you mid-dive.

A difference between the Puck Pro and the Leonardo is in their logbook memory. The Leonardo can store 70 hours of data to the Puck Pro’s 36-hours. The Leonardo is also slightly smaller so it can stow away more comfortably. However, the Puck Pro provides gas switching whereas the Leonardo doesn’t. Overall, the Mares Puck Pro is very comparable to the Cressi Leonardo, so you can go for either one.

Check out our full review of the Mares Puck Pro here.

Aqua Lung i300C

The Aqua Lung i300C is a fantastic entry-level dive computer that can also double as a backup. It has an interface that is intuitive and versatile, with some advanced functionality for those looking for features above the entry-level.

With the i300C, you have access to four modes which allow you to dive with both normal and enriched air. These modes are air, nitrox, gauge, and free dive mode. The i300C is water-activated, so if you enter the water without any particular mode selected, then it will default on air diving mode.

Next, the interface of the i300C can be navigated with only two buttons. Additionally, this dive computer has an automatic altitude adjustment feature to configure the algorithms based on your height above sea level, which it automatically detects.

We also liked how the i300C has wireless bluetooth connectivity so that you can easily update its firmware and get the latest features. You can also easily transfer all of the dive-related data to your smartphone using the DiverLog app. This way, you don’t have to worry about losing your data when you change the user-replaceable batteries. Also, you can use the phone app to change the settings on your dive computer if you find it more convenient.

Overall, the Aqua Lung i300C is a small and compact wrist dive watch with slightly more features than an entry-level dive computer. It stows nicely into a BC pocket and has a large enough display for you to easily check on the current dive data.

Oceanic Geo 2.0

The Oceanic Geo 2.0 is a classic, tried-and-true dive computer that you can’t go wrong with. As a backup, you are getting quite the bang for your buck. The Geo 2.0 is small and comfortable enough to be worn as an everyday watch. It has a puck design with four menu navigation buttons around the outside bezel.

Looking at the display, we found it to be easy to read from with each piece of information organized neatly and concisely. Its backlight is bright enough to be read even in low-vis conditions. With the four navigation buttons, there is a possibility of forgetting which does what. However, once you are accustomed to it, it provides more functionality with less button presses compared to one or two button devices.

Furthermore, the Geo 2.0 allows you to switch between two dive algorithms for greater compatibility with your main dive computer. These algorithms are the Pelagic DSAT and the Pelagic Z+ (based on the Buhlmann ZHL-16C). The Geo 2.0 has four operating modes: Watch mode, Norm (Air and Nitrox), Gauge (bottom timer), and Free (for freediving). The nitrox mode supports two mixes up to 100% oxygen.

The biggest downside to the Geo 2.0 is its small logbook memory which only records 24 dives. Also, some of the graphs can be difficult to read from the display. However, overall the Oceanic Geo 2.0 provides great value as an entry-level to mid-range device, and also as a backup dive computer.

Scubapro Digital Depth Gauge 330m

This is not a dive computer, however it can be a great backup to one. It is a depth gauge and bottom timer in one. It’s been around forever (since 1989), it lasts forever and it’s cheap enough to be replaced without much hassle. On top of its depth and timer functionality, the ScubaPro Digital 330m also provides ascent speed and temperature data.

With a massive 330m (1,082 ft) water resistance rating, you never have to worry about if this device can withstand the water pressure. It automatically activates in the water and turns off of it, so you can just focus on diving while this thing keeps working in the background. The built-in memory can store data of your last 9 dives for future review and planning.

Whether you’re a beginner or a veteran tech diver, the Scubapro Digital 330M can be counted on to track and display your dive data no matter what the conditions are.

Which Backup Devices Should You Get?

If you have the funds for it, you can literally just buy two of the same dive computer and use one as the primary device and the other as a spare. With that said, this may be too costly of an expense, or perhaps you would rather have a smaller dive computer or a cheaper alternative in which case you have a few options.

First things first, whenever you upgrade to a new dive computer, don’t retire the old one; it may be past its glory days, but it hasn’t outlived its usefulness. Keep it around as a backup! If it is an older product from the same manufacturer as your new one, or if it uses the same algorithm, then there should be little to no discrepancies in its calculations and it is thus a viable backup.

Keep in mind, when diving with a main and backup dive computer, to bring both computers on all of your dives. This allows them to accumulate the same data and build up an accurate dive profile. Otherwise, the calculations that your backup device gives will be inaccurate because it doesn’t have enough data to work with.

You don’t even necessarily need a backup dive computer. A simple, analog dive timer (also known as a dive watch), and an analog depth gauge should be adequate and will let you log the dive. There are even dive watches with built-in depth gauges so you can have both in one device. Combine that with a dive slate, and you have a perfectly sufficient scuba setup.

It’s still recommended that you end your current dive and head back to reassess your predicament as soon as possible. However, with a dive watch and depth gauge, you have the ability to perform subsequent dives, albeit with less data.

Why You Shouldn’t Rely on Your Dive Computer

Whenever a dive computer fails and you’re relegated to an analog backup, you must ponder the question: was I relying too much on my dive computer? There was a time when dive computers didn’t even exist. Now they are an invaluable piece of scuba equipment, but it has also made many divers lazy. They let the dive computer tell them what to do and when and they no longer think for themselves. Whenever a dive computer fails, it’s time to go back to scuba diving basics.

First, for deep dives, you should already have an ideal of how deep you plan on diving and approximately how long your bottom time will be. Of course, monitor your SPG to know exactly when you should surface. However, just having an estimate of these numbers can make the difference between a successful dive and a failed one.

For each dive, note down the maximum depth and time of that dive on a wrist-mounted writing slate. You should have something like this from when you took your first dive course. This way, if the dive computer suddenly fails, you can use these numbers as a reference and go on subsequent dives with just a dive watch and depth gauge. You will go no further than the previous max depth, and end your dive around the same time noted on the writing slate.

If you have a spare dive computer handy, then it’s just business as usual. However, analog bottom timers like a dive watch are a viable alternative and they are cheaper than buying a second dive computer.

Furthermore, the main point still stands. While modern dive computers can do complex calculations that the human brain cannot compete with, and they are generally reliable, you should still have a mastery over scuba diving basics. A dive computer should be an extra layer of security on top of your repertoire of skills, and should not be used as a crutch.

Best Backup Dive Computer Buying Guide

Brand

When selecting a backup dive computer, it’s worth noting that any computer from trusted manufacturers such as Shearwater, Oceanic, Suunto, Scubapro and such, are completely safe.

Furthermore, when upgrading to a new dive computer (or purchasing a backup), it’s recommended that you buy a product from the same brand as your old one. Dive computers from the same manufacturer often use the same algorithm to calculate your saturation. They also have the same dive time and surface intervals – key features of any dive computer.

When you are diving with two dive computers each from a different brand, try to find ones with similar conservatism levels. Unfortunately, since dive algorithms are trade secrets, it can be difficult to compare dive computers from different brands. At the very least, try to get dive computers that run the same algorithm. If not, then your guess is as good as ours as to the calculations it’s doing.

Next, even if you buy a “budget” computer for a backup, you can be sure that its quality and reliability is no less safe than your main one. There will be little to no discrepancies in the dive profile it creates. In the event that your main dive computer fails, your backup dive computer will have virtually identical data and calculations ready for you to resume diving as if nothing happened.

This begs the question: what exactly are you paying for when getting an expensive dive computer? You’ll generally get air integration, better displays, more points of data tracking, and other nice-to-haves. While the backup computers we recommend do not necessarily have all or any of these features, they will still provide the basic options for you to safely dive at an affordable price.

Size

Most of the time, you won’t need to look at your backup. If you’re bored and want something constructive to do during a safety stop, you may want to look at it to compare its readings against your primary. Otherwise, it’s going to spend the majority of the time tucked stowed away in your BC pocket. You might also attach it to low pressure hoses or wear it on your other wrist for easier access.

Wherever you decide to place it, make sure it’s small enough to be out of the way and that it doesn’t snag onto anything. Smaller watch dive computers can help maintain a slim profile so that you can keep it with you at all times without increasing drag.

Water-Activated

It’d be a pain having to manually activate two dive computers at the start of each dive. Try to get a backup dive computer that will start tracking your dive data on its own so that you don’t need to worry about it.

Display

Even though the backup dive computer should ideally be compact, it must also have a large enough display so that you can read from it with a mask on, potentially in low-vis conditions underwater. That means that the font should be legible, the layout clear to understand, and the backlight bright enough (and easy to activate) so that you can read it at all times.

User-Replaceable Batteries

The batteries on most dive computers can be easily replaced by the user. It’s up to you to decide when to change the batteries. We’ve heard of divers who replace the batteries on their main and backup computer at different times so that they don’t both die at the same time. Some divers change the batteries before each trip.

Keep in mind that depending on the dive computer, removing the battery may wipe all of the data currently stored on it. Be sure to backup the data to your phone or computer before replacing the battery. Some dive computers can retain the data between battery changes, which is convenient.

Alarms

You may not want your backup computer to have loud alarms. Some models allow you to disable most or all of the alarms on the device. Others provide haptic (vibrating) alarms so that you can disable the beeping and flashing, but retain the haptic alarms if you so choose.

Lockout Features

A big no-no, particularly if you are an experienced diver, is getting a dive computer with an automatic lockout feature. How it works is if you ascend too quickly or miss a required decompression stop, then the computer will lock itself so that you are forced to end the dive.

The lockout “feature” was designed with good intentions, but it has done nothing but make a lot of divers very angry. It’s like if your car decided to shut itself off because you went over the speed limit. Imagine spending hundreds of dollars for a sophisticated piece of equipment that decides to send you to timeout for not listening to its instructions like an overbearing parent.

Suunto dive computers are infamous for locking out their users. There is a joke that you shouldn’t even shower with a Suunto dive computer on your wrist because you’d risk locking it out. Obviously this is greatly exaggerated, but the point stands that it’s probably not a good idea to use a Suunto device for a backup.

Furthermore, some divers have found that they were forced to rely on their backup computer because their primary one locked the user out because they ascended too quickly. It’d be really bad if both of your dive computers had this feature (i.e. you brought two Suunto devices); then you’d really be SOL.

Travel Tips

When packing your dive computers, consider putting your primary dive computer and your backup in separate bags. This way, if airport security decides to hold onto one of your bags and deliver it after your flight, or the bag gets lost/delayed, you’ll still have one dive computer in another bag to use.

Best Backup Dive Computer: Summary

Dive computers are a crucial scuba diving tool these days. Instructors will recommend a dive computer as one of your first purchases if you’re just getting started. However, dive computers are a costly piece of kit, and now you are being told you may need a second one? If you are looking to get yourself an affordable dive computer and you don’t want to take out a second mortgage, there are still options available which we discussed in this article.

In our list of recommendations, we provided some affordable options that can be used as a backup dive computer. Furthermore, we even provided some alternatives to dive computers, which are dive watches and depth gauges. Dive watches are generally more affordable and some of them even have a depth gauge built-in. Otherwise, you can get a dive watch and depth gauge separately, and the cost should still be less than a dive computer.

You may be wondering if a second dive computer is worth the expense. The answer is a resounding YES. Whether you are judging this decision from a financial cost point of view, or a safety point of view, having a backup dive computer is very much worth it.

Imagine going on an expensive vacation or liveaboard only for your computer to die at the part way through. Without a backup dive computer monitoring your exact dive profile, you are expected to end the dive and take 24-48 hours off from diving to desaturate. Even when you get a rental replacement computer, you’ll have to start a fresh profile which may be inaccurate for the first few dives.

If you simply had a backup dive computer, you can just swap to your backup and continue diving with no issues. Think about how costly it is to miss out on 1-2 days of your vacation or liveaboard; it’s likely much more expensive than the cost of a cheap backup dive computer. This is one of those situations where it may be cheaper in the long run to spend more money now.

Even with just a bottom timer and depth gauge, you can technically continue diving if you use a decompression table to calculate how deep you can dive, how long you can stay at that depth, and when you should perform safety stops. This is what divers in the past had to do before dive computers became mainstream, so basically you’re going old-school.

Whether you decide on getting a backup dive computer or use a dive watch with depth gauge, the point is, you need to have some kind of redundancy to stay safe and save money in the long run.

Last update on 2024-04-23 / Affiliate links / Images from Amazon Product Advertising API