My Detailed Initial In-Water Impressions of Garmin Mk3i

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Question: has your mk2i battery life degraded substantially over time? I have an mk2i and I only charge it to ~80% because I read on the internet that charging it all the way to 100% on a regular basis will wear out the battery prematurely. Years later my battery is like new, but of course I have no idea whether that's because I don't charge it beyond 80%, or whether it would have done just as well even if I was regularly charging it to 100%. As someone who charges to 100%, what have you observed?
I’ve been daily wearing my Mk2i and diving it regularly pretty much since it came out; the battery is a little degraded, but I’m still charging maybe twice per week. That’s with daily wear, 4-5 GPS activities (running, MTB), and probably 2 dives per week.
 
The biggest difference between the T1 and T2 is the ability to use the diver-to-diver messaging system, which I don’t see as being a useful feature, but maybe someone will prove me wrong.

You can also connect more T2 transmitters to one computer (8 max vs. 5 with the T1). Again, probably fairly useless except for the one or two instructors in this world who will actually buy 8 of these things. (See here for details: Garmin Dive Computer and SubWave Network Air Integration Transmitter Compatibility | Garmin Customer Support)

I will not be buying a T2. In fact, I may buy another T1 as I’m already seeing their prices drop. As I said in the review, the Mk2i/T1 combination worked flawlessly for me over 90 dives, so I’m not exactly aching to upgrade the transmitter.

Thank you for this! In all my research on the Descents to date, I had not seen this compatability chart mentioned anywhere else. I'd assumed you needed to have the specific transmitter for each watch, and knowing that they're cross-compatible is fantastic.
Though I agree that not having it be MH8A compatible is a pity.
 
So, I figured I would take a few minutes to write up my initial impressions of the Garmin Mk3i after my first dives with it since there don’t seem to be any in-water reviews on Scubaboard yet (In fact, I find it odd that there are still very few reviews anywhere on the Internet), My review will focus primarily on the differences between the experience diving with “old” Mk2i vs. the Mk3i. I hope it will be helpful to those who have used the Mk2i and are considering an upgrade or those who might be on the fence about the Mk3i versus other options on the market (including the currently discounted Mk2i). I will not focus on the overall features of the Mk3i because many videos on the web go pretty deep into this.

Background
I’ve been diving the Mk2i over the past year and have 90 dives on it. I’ve pretty much brought it through the wringer on open-circuit dives - shallow, deep, multi-gas deco, and gauge-only. I don’t dive CCR, so I can’t comment on that. I dive with the Garmin T1 Transmitter for air integration (for reference, the Mk3i was introduced alongside the new T2 Transmitter - more on that later). Most of my diving is warm water wreck diving in Florida, but it’s come with me to the Bahamas, Cozumel, Maldives, and French Polynesia.

So, full disclosure going into this: I have really liked the old Mk2i. I feel that the functionality and the software are robust, the unit is rugged as hell, it has amazing battery life, and it has a good online services ecosystem with Garmin. The bottom line is that the Mk2i + T1 transmitter did not let me down over 90 dives. I also like the wristwatch form factor, although I am highly aware that this is a very personal preference and a frequent topic of debate among the community - I won’t go down that rabbit hole. So, of course, I was excited to try the new Mk3i given my good experience with Garmin over the past year.

View attachment 824383
[Older Garmin Mk2i on the left, new Mk3i on the right]

Initial Impressions
It’s probably no surprise that I’ll start with the screen. The AMOLED screen in the Mk3i is a MAJOR improvement over the Mk2i. It is bright, crisp, and clear and doesn’t leave anything to be desired. According to the specs, Garmin had finally cracked the code when it comes to offering this type of screen while simultaneously preserving the amazing battery life that the Mk2i offered (actually, improving on it in this new model - I’ll speak more to this in a bit). The Mk3i now also comes with a touchscreen that allows you to tap and swipe the screen. However, I have rarely used it. The button-based navigation scheme introduced in the Mk2i has carried over to the Mk3i, and it’s been burned into my brain at this point, regardless of how archaic it can be. The screen size has not changed, but it appears slightly larger due to the Mk3i’s slightly thinner bezel.

The unit itself feels rugged and well-built. It’s a tank, but it doesn’t feel heavy on the wrist for me. It looks and feels like a very premium product. The new strap looks and feels identical to that on the Mk2i, and I like how it’s both somewhat soft but still very strong. The tactical push of the buttons feels the same, but they have added some new type of safety guard to the Mk3i, presumably to protect the most important “Start” button, which can be used to stop the dive or switch gasses, among other things.

I think the last major physical attribute of note is the addition of the LED “flashlight” to the case edge just above the top strap. The light is surprisingly bright for what it is, but I’m not sure it’s a feature I’d see myself using a lot - perhaps while on the boat during the occasional night dive. To be clear, this is pretty useless underwater. It’s a cool addition, but not one that excites me too much.

View attachment 824453
[New Mk3i on the left with "button guard". Mk2i on the right.]


Software and Setup…and lessons learned after Dive 1!
The setup was easy, as you would expect from Garmin. I would like Garmin to pull settings and preferences from the cloud every time you set up a new device, similar to what Apple does for most devices. Unfortunately, you must set the Mk3i up from scratch, even if you have a previous Garmin dive watch. Unlike the previous computers, the Mk3i will now default to the “Big Numbers Mode” screen layout. For about my first 70 dives on the Mk2i, I avoided this screen layout because I thought “more data was better”. But I often found myself squinting at the screen and searching for what I was looking for. In reality, I think the Big Numbers layout is more practical, easier to read, and covers everything you’d need: Depth, gas type, NDL, PO2, Run time, descent/ascent indicator, air-integrated PSI and a revolving upper “panel” that can be tapped to rotate in a few other data elements, such as water temperature. The screen contents will dynamically change depending on the circumstances. For example, NDL is replaced by a bright green box that contains your safety stop countdown once you hit 20 feet or your customized depth trigger.

I should note that I did not buy the new Garmin T2 transmitter and decided to use my “old” T1 transmitter instead. (See below, where I talk more about transmitter compatibility) However, I missed one big key setup item, which is not explicitly mentioned in the documentation: You must set up all cylinder attributes if you’re using air integration, even if the transmitter was previously set up correctly. This makes sense when you think about it, but in my head, I just assumed that the transmitter would know that I was using a 100 cu. ft. tank with a working pressure of 3442psi because that is how it was always set up. However, the transmitter itself is pretty dumb and just sends the current PSI data to the computer, which is the real brain of the operation. Garmin defaults the transmitter settings to 3000psi working pressure and a cylinder size of 0 - yes, zero. As a result, my numbers were screwed up after my first dive, most notably my computed SAC and recorded cylinder attributes in the computer’s Dive Log and Garmin Dive app. During my surface interval, I changed the AI settings to the correct cylinder attributes, and everything worked correctly on the second dive. (Suggestion to Garmin to set the default AI cylinder settings to something typical like 77 cu/ft. + 3000psi for an AL80)

Automatic syncing to the online Garmin Connect service and Garmin Dive app worked right after setup. When I grabbed my phone during my surface interval, I had already been notified that the first dive was uploaded and available. The Garmin Dive app is one of my favorite components of the Garmin offering. It's a data nerd's dream

CONTINUED IN NEXT POST (Due to length restrictions)...
Thanks so much for the excellent post - have been window shopping/gawking at this computer (use a trusty Oceanic Geo 4.0, but am ready to move up to integrated; I am a daily Apple Watch user, and while the Ultra 2 is nice for diving, no integration. The features, screen, and usability for diving of the Mk3i seem ideal and will last me for quite some time. Appreciate the practical writeup!
 
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Great review. I did wear my Mk2i as an everyday fitness watch, and it worked extraordinarily well for me in that role, so I took a slightly different approach and added a 47mm Fenix 8 to get the screen for daily life, and to use as a backup computer - similar to your arrangement but a step down. I perhaps should have sold the Mk2i and bought a 3i instead, but I am certainly enjoying the Fenix 8.

I also love that your review uses the same watch face I have been using in its various iterations for almost 6 years going back to the Fenix 5!

I am one of those vacation divers that Garmin converted from Suunto. I retired my Fenix 5 and gave my daughter my Vyper Air when the Mk2 was released, and am firmly in their ecosystem for running, cycling, and overall health and fitness tracking, in addition to diving. The Mk2i has been a joy to use, and I am looking forward to diving with the Fenix as well in 2 weeks on Spiegel Grove.
 
Question: has your mk2i battery life degraded substantially over time? I have an mk2i and I only charge it to ~80% because I read on the internet that charging it all the way to 100% on a regular basis will wear out the battery prematurely. Years later my battery is like new, but of course I have no idea whether that's because I don't charge it beyond 80%, or whether it would have done just as well even if I was regularly charging it to 100%. As someone who charges to 100%, what have you observed?
Yea I think I am one of the paranoid types that shoots himself in the foot by charging my Mk2i 100% far too often.

I feel like over last two years I noticed a decline in the battery, but here is a bad news/good news caveat - the haptic vibration feature crapped out a few months outside of warranty. It made a just loose TicTac sound rather than a tight vibration. I called Garmin to inquire abut repair and to my surprise they covered it by sending me a NIB exact replacement. This may have been because it is an internally known issue, or maybe due to the pending release of the Mk3 at the time, but either way it exceeded my expectations to be covered that way.

I will try to have the discipline to avoid charging to 100% except on dive vacations where I will go back to being neurotic about it. :)
 
My review of the Mk3i 51mm with the T2 transmitter.

Bought June 2024, Fairly active use above water and I’ve made 25 REC dives with it.


First of all, it's horribly expensive. I paid about EUR 2000 for the set and it took me a couple of months to justify this to myself. I wanted a watch style computer with AI. I already had a Suunto D6i with pod that was fine, but the screen became more and more difficult to read in the murky Dutch waters with my ageing eyes. So I wanted a really bright screen. That meant I either had to buy (at the time) the Teric, Tern TX or the Mk3i. The Teric is of course great, but I had it on my wrist and I found it too chunky. So that one didn't make it. Tern TX was a real contender, but I found it lacked good looks and was rather expensive for the limited above-water functionality. At the end I chose the Mk3i because of the overall functionality (dive computer, smart watch and sports activity watch), even though it was by far the most expensive option. Although in size the mk3i and the Teric differ little in size, I find the Mk3i to be big on my wrist, but not too big (I'm of average size).


The standard strap is fine, nothing bad about it, but it doesn't have the high-quality feel to it that the rest of the watch does have. To be honest, I'm not sure what that high quality feel should be with these kinds of straps, but it was something that stood out. The Mk3i uses the Garmin quickfit-method of attaching straps and it is great. Detaching a strap is done in 2-3 seconds without any tools and it's a reliable way of attaching. Garmin also provides an additional strap for use with a wetsuit or drysuit. What struck me was the fact that this strap is inordinately long. I wear a 7mm wetsuit and wear it over my suit. Then the strap is still much too long! I'v even considered cutting a piece off, but that goes too far. It is a nuisance. Garmin provides a large number of different straps that look great, but are also ridiculously expensive. I've bought a number of very nice straps at Amazon that work great at a fraction of the price.

The watch is black and of course chunky, but not in a bad way for me. I wouldn’t wear it under a suit, but in any other social setting I feel fine wearing it. There are some dark blue accents around the buttons that look good without being ostentatious. The buttons have a very solid, nice feel to it and function very well, above and under water and with and without gloves. My one gripe about the buttons is the fact that the activity button is built slightly different and -possibly because of that- I quite often have accidental activities started. Maybe it’s a bit too sensitive and of course the large size doesn’t help. The whole device is built like a tank. After 7 months of use (including bumping into stuff, falling, etc.) the watch still looks like new.

Now the screen. Many others have said it, but it’s absolutely fabulous. Very bright, high contrast and therefore very legible underwater. It can be toned down or set very bright and I’m very happy with it.

At first I thought the built-in flashlight was a nice gimmick, but nothing more. I have to be honest, I use it almost daily to look in a dark corner in a closet or walking around at home at night in the dark. It’s very handy, has several brightness settings and overall gives a surprising amount of light. Not underwater of course. There it does little and is only usable if you have nothing else.

The general software and functionality of the watch is next to identical to the Epic and many other Garmin products and that’s good. From an activity point of view, it can do pretty much everything and I mainly use it for walking and hikes. Also in Sweden where I downloaded a specific hike that took me exactly where I needed to be. Very good and very accurate. I am surprised, by the way, about the amount of preloaded walks. I was doing a small hike through some forest and it immediately picked up the directions and they were spot-on.

The diving app and the diving functionality of the Mk3i are good. The app is clear and logs about everything you want and you can easily use the app as a logbook for your dives. Garmin has struggled a bit with correctly displaying SAC rates, but it now seems to be working fine.

The watch provides quite a few options while diving. I opted for the standard more limited data presentation, but with larger fonts. I displays all the info I need and in a logical way. There is an option to build your own screen and that may work great for divers with specific (TEC) needs, but I would have liked to have the opportunity to completely build my own screen. So as a dive computer (for recreational use) it functions great. For TEC use, I have no idea.

I bought the T2. That works like any other pod, which is fine. I have had no issues with hearing beeps while underwater, but that’s probably just age or the loud music I sometimes like. I’ve never tried the underwater messaging as this is part of the reason why I’m underwater: peace and quiet, no messaging, relax and look at beautiful stuff. So no thank you for me, I’ll stick to hand signals.

For smartwatch use, it’s very nice. It’s not an Apple watch so it’s a bit more limited, but the Garmin app store has some nice apps and thousands of watch faces. The built-in ones are nice, but in practice I use custom ones as I find these even better looking. Some are free and some are not. I think I regularly use three different watch faces and that cost me eur 10 or something in total. Yes, it’s expensive, but considering the total cost of the watch it’s negligible.

Battery life is spectacular. Normal use is 30 something days before charging. I use the always-on function and constant heartrate monitoring and I still get about 8 days of use on a charge. Diving takes up a little more energy than normal use, but you can dive quite a lot on one charge. The actual usage seems comparable to factory lists.

So all in all, to me, it’s a fantastic dive computer with a ridiculous dive strap, a great activity watch and a good smartwatch, which is bloody expensive, but it’s very good and sturdy. At the moment there is also the new Suunto with a much lower price tag that should provide serious competition. Also, for those not needing AI and only wanting rec diving, there is now the Garmin Fenix that’s probably attractive to others (also much cheaper). Is the cost worth it for you? That’s entirely up to your needs and budget. Knowing what I know now, I would still buy it.
 

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