Vandit Kalia, 25 July, 2025
Based out of Italy, Ratio has been slowly and steadily making a name for themselves as a maker of very robust, full-featured dive computers, with many divers swearing by them as a credible alternative to Shearwater.
Now, those of you who have dived with me know that I am a huge fan of Shearwater computers and we recommend them without reservations for anyone looking for a dive computer, regardless of level. So when I had 2 experienced dive buddies recommend Ratio, it piqued my interest. And luckily, Ratio is now available in India – so I requested a couple of units to test and review. A week later, I had a couple of demo units in my hand for review, and took them to our weekend diving camp in Pondicherry, where I put them through their paces.
Disclaimer: the units I am testing have been sent to me for review and I will be returning them after the review is done. No large sums of money changed hands (unfortunately).
In this article, I will be reviewing the Ratio iDive Color, a wrist-watch sized dive computer designed more for recreational diving but with plenty of tech features also available. I have a separate review of the Ratio iX3M2, their oversized tech-focused computer published on the site as well, and where relevant, I will highlight some of the differences between the two models in this article.
[Video review of the computer coming soon]
FEATURES
This is a wrist-watched size dive computer with a 1.3” display, that’s somewhere between a Garmin Descent G2 and a Shearwater Teric in size. This line has 2 models, the iDive Sport, with a backlist black and white display, and the iDive Color, with an ultra bright color screen. Within each model are 3 variants – the Easy, the Deep and the Tech+.
The Easy model is designed for primarily for recreational diving, while the Deep and Tech units add various tech features. While I will touch upon those features, I am not going to spend too much time talking about them, because a small, watch-sized dive computer is not the tool you will use for tech diving, no matter how many features manufacturers pack into them. If your goal is serious tech diving, you need to look at the iX3M2 in Ratio’s product line (or the Perdix over the Teric in the Shearwater line).
Let’s get the obvious features out of the way. Like virtually every computer these days, the iDive Touch Easy has gauge, freediving and nitrox modes. And it comes with 2-factor alarm – visual and acoustic (but no vibrate mode, unlike the iX3M2) – you can set alarms for ascent speed, MOD, gas reserve (if using a transmitter), NDL, deco violation, time and depth. At the end of the dive, the computer also displays your Desaturation Time as well as your surface interval duration.
It also has a built-in compass, although this compass lacks the extreme tilt compensation of the iX3M2 model. For typical recreational purposes, this should be good enough and really, how hard is it to hold your arm somewhat level?
The computer also allows you to switch between 2 gas mixes, unlike the iX3M2, which allows up to 3 gas mixes. This lets you do moderate deco dives with a single deco cylinder – and that’s really about as far into tech you should be going with a watch-sized dive computer. And the iDive Color is also compatible with Ratio’s unique air transmitters, and can be paired with 2 wireless air transmitters as well.
For some reason, the iDive Color seems to use the Buhlmann ZHL-16B algorithm, an older variant designed more for use with dive tables. I am not sure why Ratio decided to go with this instead of the more typical ZHL-16C, which is designed for dive computers, but the net result for this is that you, as a diver, will get more bottom time as a result of this computer. The good news is that if you so prefer, you can always make the computer more conservative by using one of the 5 other settings (for a total of 6), which should more than offset this difference. And one cool thing
It has an NDL planner that will let you plan a dive and show you how much NDL you will have left at the end as well as how much air is needed for that dive. In addition, it also has a deco planner too, which uses your planned profile and gas mixes to prepare a run table (albeit without validation of CNS, potential of counter diffusion or gas volumetric availability).
Like with iX3M2, you can purchase an optional analyser accessory that plugs into the unit and lets you set the computer directly from the testing unit – attach one end of the accessory to the computer and use the analyser on the other end to test your Nitrox mix, and the number will show up on your computer, for you to save. Super cool!
The Deep version of the dive computer adds the following features: ability to use up to 3 gases and 3 transmitters, handling of normoxic trimix and a choice of 2 algorthims (Buhlmann Z16C and VPM-B)
The Tech version adds full trimix, ability to use up to 10 gas mixes and 10 transmitters and user settable Gradient Factors & Critical Bubble Radius
As with the iX3M2, it is a mildly annoying to have to pay for the top version to get user settable gradient factors when an entry level Garmin or Shearwater lets you do so just as easily. But atleast you can upgrade to a higher feature set simply by plugging the unit into Ratio’s Toolbox app and applying an upgrade code (purchasable online) to do so. The Toolbox app also lets you customise the unit a little, download your dives, install app upgrades and more.
Lastly, the unit comes with a rechargeable battery that uses a USB cable with a proprietary locking connector on the other end. This connection is very secure and ensures that the unit won’t accidentally come loose. That’s pretty much standard for watch-sized dive computers.
SET UP
The iDive Color uses a 4-button system for navigation, with two buttons for up/down or +/1, one for enter/confirm and one for back. They aren’t labelled, however, so it may take you a couple of tries to remember which is which (especially if you have a 4-button device from a different manufacturer, like I do). But once you get the hang of it, it is fairly easy to navigate and set-up.
Initial setup will consist of setting the date and time (easy enough to do) and configuring the display – specifically, the brightness of the backlight, the sensitivity of the “rotate to wake up” feature (by default, the computer screen goes blank after a certain period of inactivity and can be brought back to life by rotating the wrist) as well as collars of the alarms, data and labels.
You can also program in your preferred degree of conservatism, toggle between salt and fresh water, metric vs imperial, set up your various alarms, set the depth and duration of the safety stop, whether you want to add in deep stops or not and, to the chagrin of the DIR crowd, the depth of the last deco stop (IYKYK).
Once you get the hang of the buttons, this whole process takes a handful of minutes.
USE
While I am a big fan of wrist-watch sized dive computers for the simple fact that you can wear and forget them when you go diving (and that includes keeping them on while taking/removing your wetsuit), the display is most certainly not as intuitive as on a mini-brick sized dive computer. And that certainly holds true for the iDive Color.
I mean, look at this:
Thankfully, Ratio chooses to display the most important display of the unit (the NDL) in a large, visually distinctive size, with depth and dive time also fairly clearly separated from other info.
As a default, the computer displays the mix and PPO2 on the bottom of the screen (with the mix flashing in red if a better mix is available). However, you can cycle between this and other indicators like stopwatch, temperature, average depth, ascent or descent speed, max depth, OTU/CNS, algorithm and conservatism setting.
You can also cycle the entire screen to also show a compass, tissue saturation levels, a graphic profile of the dive to date and a deco table (if you have gone into deco).
The compass mode is very intuitive to use, and you can lock in a compass bearing, which is displayed at the bottom, along with its reciprocal. In addition, a visual indicator lets you know if you have veered off course, by pointing out which direction you should turn to compensate. And of course, depth and time are displayed at the top of the screen, although NDL is not.
One thing to note about this (which also holds true for watch-sized computers): they rely heavily on icons as labels – after all, there is only so much text you can fit into a small 1.3” display. The downside is that these icons are not always very intuitive / easy to understand. Take this example of the display when it shows the graphic profile of the dive:
At the bottom of this screen, you can see a bunch of information – do note the iconography to denote what’s what. You definitely need to read the manual to understand that, especially the first few times you have the computer. While the actual data on the numbers may help you guess what they indicate, you shouldn’t need to rely on guesswork to understand your computer. Also note the fact that the bottom left number (45 in the image above) can be either NDL or deco info, depending on your status, without any way to distinguish the two. Why? That’s just asking for confusion, especially with newer divers. Not to mention whether it is meant to be “stop at current depth” to “time to surface”, if you are in deco.
This gets more confusing when you are doing a safety stop, as the display starts showing a lot more info, as shown below:
And don’t get me started on deco:
As you can see, there is a lot of information crammed into a small screen. Some of it is a natural byproduct of the form factor. Some of it is a byproduct of manufacturers choosing to pack in a lot of features into the device (and Ratio is by no means unique here). And some of it is also a design choice – for example, I feel the data would be a lot easier to understand if Ratio put “m” or “ft” at the end of numbers indicating depth, and added a “:” before numbers indicating time: so “:20” instead of “20”. Again, to be fair, familiarity and usage will overcome this confusion, but for divers who don’t dive that regularly, the easier you make the displays, the better it is.
One neat feature of Ratio computers, including iDive, is that you can change a lot of the settings (mix and conservatism) during the dive itself, to account for user error and/or change in dive circumstances. That’s pretty handy.
After the dive is over, the computer displays the desaturation time, no fly time and surface interval.
Lastly, the claimed battery life of the unit is 20 hours and in my testing, after 3 days / 8 dives over a weekend and then a week of being in sleep mode and still had 50% charge left. So you should easily get 5-6 days of diving out of it, although the exact amount will depend on the brightness, display settings and whether or not you are using transmitters. That’s better than similar computers with AMOLED screens. Since I am not watching 4k movies on my computer and the IPS display of the iDive Touch is more than legible enough, even in really murky waters, I’ll happily go for the longer battery life here than a super high-tech screen.
SUMMARY
So what’s my overall evaluation of the unit?
Well, despite my reservations on the complexity of the display, that is a tradeoff that you make when you choose a watch-sized dive computer, especially one packed with as many features as the iDive Color. Even the Garmin and the Shearwater watch style dive computers are not as intuitive as their bigger brethren. These are not fatal flaws – for recreational diving, you need to get familiar with a couple of screens at most, and that will come very easily with some dives.
For technical diving, where you may be task loaded with other things, that small screen crammed with information is a very bad idea. That’s why I started this article with the statement that watch-sized computers are not for tech. Sure, you can do “light tech” (single deco cylinder, air and moderate deco obligation) with this, but for anything substantive, it is better to get a brick-style dive computer.
For recreational divers, however, the Ratio iDive Color gives you excellent battery life, a bright legible display, a compass, air integration, advanced dive planning mode and all the conveniences of a full-featured dive computer. What’s not to like? Recommended.
