• Tony

Review of the Garmin Descent MK2i

The long awaited Garmin Descent MK2i dive watch is here! I have my hands on one of these new computers, and would like to share my thoughts on it. How does it compare to the Descent MK1? How well does it work as a dive computer? How does it compare to the Shearwater Teric? Is the price point worth it? Let's find out.

My Garmin Descent MK2i.
My Garmin Descent MK2i.

For those unaware, Garmin came out with their first diving watch, the Descent MK1 several years ago. It’s a watch-style fitness device, made for scuba divers. As a runner I had always been a fan of Garmin fitness products, however I was very nervous as to how their first dive computer would function. As it turns out the diving 'app' as Garmin calls it, is quite outstanding and well thought out. Much has already been written about the Descent MK1. So the question is, how does the MK2 improve on this? 

The 2 computers are almost identical, in size, shape and weight. For fitness users, the Descent MK2 adds a few new things like pulse oximetry, and some new metrics for your workouts. 

Air integration 

The biggest addition for the Descent MK2i (the “i” stands for integration, in case you couldn't figure that out) is what Garmin is calling the subwave network. This means your wireless air integration transmitters use a sonar-based communication technology instead of the radio-frequency method used by most other computer manufacturers. 

Product photo of the Garmin Descent MK2i with wireless air integration transmitter.
Product photo of the Garmin Descent MK2i with wireless air integration transmitter.

Subwave is good news and bad news for some divers. The bad news: the wireless transmitter is proprietary to Garmin. Any existing transmitters you may have from other dive computer manufacturer are incompatible with the MK2i.

The good news: Increased range and signal strength underwater, as well as support for up to 5 transmitters. Garmin claims up to a 10 meter or 30 foot range, which from my limited experience with it, seems actually conservative. The combination of increased range and the number of supported transmitters could actually allow one to monitor not only their own air pressures, but also the air pressures of those around them - something the MK2i supports.

In theory, this idea is really cool. For a dive center willing to spend the money on a bunch of transmitters, a dive instructor or dive guide could conceivably monitor the tank pressures of a group of student's or DSD's. In reality however, I don't see many dive centers willing to cough up almost $4,000 worth of gear just to help monitor tank pressure, and the odds of having all of your paying guests similarly equipped are probably nil.

Garmin isn’t unique to the idea of sonar pulses for transmission of air integration data. Fans of the dive computer company Liquivison will remember that the Lynx dive computer also employed a similar idea. The technology allows for some amazing potentials, such as location, ranging, and the ability to send text messages. Yes, I know most of us dive to escape the nagging of text messages, but for emergency or diver recall situations, this could be useful. Neither location services or messaging have been implemented on the Garmin, but it's something that could be at a future date.

A Liquivison Lynx dive computer, showing underwater text messaging.
Anyone remember the Liquivision Lynx? Apparently, I was its bitch. This was a demonstration of the Lynx's underwater text messaging feature as shown at DEMA 2012.

It's worth noting, that Garmin is making 2 versions of the Descent MK2 - with and without air integration. The “i” version is available only in a titanium bezel, while the standard MK2 is available in stainless steel and titanium, but only the MK2i will support wireless air integration.

The Garmin MK2/MK2i diving modes

For those unfamiliar, Garmin’s fitness activities are programmed into their watch in what they call apps or activities, and the diving modes are no different. There are dozens of pre-loaded apps and activities for any outdoors enthusiast, but for the purposes of this review, we will stick with the ones related to diving. Both the Descent MK1 and MK2/MK2i support the following dive activities: 

Single Gas - This is intended for most recreational, single tank divers, although it does offer the ability to change to an alternate gas mix while underwater of up to 100% oxygen, and will support full decompression, should you inadvertently miss your NDL time. You can enable or disable a missed deco lockout period. 

Multi-Gas - This mode is for open-circuit technical divers, and allows for up to 6 preset gasses of any oxygen and helium combination for back gas and decompression mixes. 

CCR - This mode is for rebreather divers of course, and allows for constant PO2 decompression calculations with multiple diluents, along with up to 6 saved bailout gasses.

Gauge - A simple gauge mode for those who wish to know depth and time.

Apnea, and Apnea Hunt - these are Garmin’s freediving apps, but as the world’s least knowledgeable person on freediving, I can’t comment on them, how they work, or the difference between the modes. 

List of apps on the Garmin Descent MK2i.
List of apps on the Garmin Descent MK2i.

Activities and apps can be added, sorted, or made 'favorites.' Both Garmin and 3rd party developers make all sorts of apps that one might find useful. You can remove the activities you don't do, and keep a short list of things you actually do.

In all diving modes, Garmin uses the Bühlmann ZHL-16c algorithm, and allows the user to adjust their conservatism using gradient factors. Garmin offers 3 preset levels of conservatism - high (35/75,) medium (40/85,) and low (45/95,) as well as a user-customizable setting. This can even be changed underwater.

Gradient factors on the Garmin Descent MK2i.
Conservatism screen allows you to choose your own gradient factors.

In every diving mode, 3 screens may be accessed:

Your main diving screen displays the basics - depth, time, NDL (or 1st deco stop) and water temperature. If you’re diving the CCR mode, it will also display your setpoint, and your diluent mix. If you have air integration, the temperature line can be replaced with up to 2 tank pressures. It will even display this in CCR mode.

Garmin Descent MK2i single gas main diving screen
The single gas mode main diving screen.

Garmin Descent MK2i CCR main diving screen
The CCR mode main diving screen.

From each main screen, the user has 2 options. Pushing lower right will bring up a menu allowing the user to change certain parameters. In open circuit mode, one can change the gas mixture, adjust their deco PO2, or edit their conservatism.

Screen in the single-gas mode that allows divers to change their mix, decompression PO2, or their gradient factors.

In the CCR mode, a lower right push will allow even more options, including switching setpoint (this can also be done automatically by depth,) bailing out, adding or editing gasses, editing setpoints, and editing conservatism.

Screen in the CCR mode, that allows for additional diver options, like changing setpoints, bailing out, adding or editing gasses, or changing conservatism.

From the main menu, pushing the left lower button will scroll you to the compass screen, where it will bring up a heading, and an animated compass strip, along with your NDL, depth and time. 

Garmin Descent MK2i compass screen
The compass screen is the same in all modes.

Pushing the left lower button again, will scroll you to the third screen, which offers some additional information. Here we can see the time of day, time to surface, water temperature, max depth, battery level, NDL, current depth, and dive time. If you’re in the CCR mode, a slightly different layout it shown, where it shows OTU level, and CNS percentage in lieu of max depth and the temperature.

Garmin Descent MK2i single-gas expanded data screen.
The single-gas expanded data screen on the MK2i.

Garmin Descent MK2i CCR expanded data screen.
The CCR expanded data screen on the MK2i.

Those with air integration enabled, can access a 4th screen, which is the AI screen. Here it shows your surface air consumption rate, your estimated air time remaining, tank pressures (which can be named,) NDL, depth and time. 

The AI screen on the Garmin Descent MK2i.
The AI screen on the Garmin Descent MK2i.

Previous versions of Garmin firmware did allow for the heart rate to be shown in the 3rd diving screen. This of course leads everyone to ask the question, how well does the heart rate work underwater? 

In my experience, not terribly well. Even though the new firmware doesn’t show the heart rate anymore (it may on the freediving modes, I’m not sure,) it still does log your heart rate. This graph shows my heart rate on one of my recent dives, and you can see how erratic the data is. Obviously the watch needs to be on your bare wrist, for this to even work at all. 

Heart rate graph from the Garmin Descent MK2i.
Heartrate graph from one of my dives on the Descent MK2i. You can see how erratic the data is. Hopefully that's not my actual heartbeat.

How does it compare to the Teric? 

Having owned a Shearwater Teric, a Descent MK1 a now a Descent MK2i, I get asked this question very often. Divers always want to know, which one is better? Which one should I buy? 

Shearwater Teric next to the Garmin Descent MK2i.
Shearwater Teric next to the Garmin Descent MK2i.

I’ll start this off by saying that everyone has their own needs from a dive computer, and mine are a bit different from most divers. All of my diving is done on a rebreather which has its own primary computer. I wear the Garmin as a timepiece first, as a fitness device second, and a dive computer last.

Since the Shearwater Teric doesn’t offer any fitness apps, it’s not really a direct comparison. So for those who are