Garmin Descent MK3i Dive Computer

Garmin Descent Mk3i dive computer

The Mk3i is the computer people buy when they are tired of wearing two devices. It is a genuine technical-capable dive computer that also works as an everyday watch, and it does not make you feel like you compromised on either half.

What actually sets it apart underwater is SubWave sonar. You can send preset messages to your buddy, see their depth and tank pressure, and know how far away they are. Nobody else does that properly yet, and once you have dived a pair of them you notice its absence on every other computer.

It comes in 43mm and 51mm cases. That choice matters more than the colour, and it is the thing we most often talk buyers through before they order. Everything in our dive computers range gets sized to the wrist it will actually live on, because a 51mm case over a 7mm drysuit cuff is a different proposition to the same watch on a bare wrist.

• 43mm and 51mm case sizes
• SubWave sonar for diver-to-diver messaging and buddy tank pressure
• Air integration with Descent T2 transceivers
• Scuba, nitrox, trimix, CCR, gauge, freedive and apnea modes
• Full smartwatch, GPS, mapping and training features on the surface
• Available with or without a transmitter

Why divers choose the Descent Mk3i

SubWave changes how a buddy pair dives

Hand signals cover about six messages and only work when you can see each other. With two Mk3i units you get preset text messages, your buddy's depth, their remaining gas, and a rough distance. On a low-visibility UK wreck that is a genuine safety change, not a gimmick. It is the single feature that makes divers upgrade from an older Descent.

One device that honestly replaces two

Plenty of dive computers are excellent underwater and dead weight on land. Plenty of smartwatches are the reverse. The Mk3i is a real dive computer first, with the training, sleep, GPS and notification stack you would expect from a Garmin on top. If you already wear a Garmin daily, this is the one that does not ask you to take it off to go diving.

It covers you from open water to trimix

Scuba, nitrox, trimix, closed circuit, gauge, freedive and apnea are all built in. You are not buying a recreational computer that you will replace when you start technical training. That matters at this price point, because the Mk3i is a five to ten year purchase for most people.

We can service and support it here

Buying a £1,200 computer from a warehouse means you are on your own when something needs attention. Every dive computer we sell can be serviced in-house at our UK dive centre, and we will pair the transmitter and set the gas mixes with you before you leave rather than sending you home with a manual.

Features in real-world use

SubWave sonar messaging

Preset messages travel between units acoustically, so no line of sight is needed. Range is short by design, which is the right trade for a buddy pair. Practise sending and acknowledging on a shallow dive before you rely on it, because the interface takes a couple of dives to become instinctive.

Air integration with the T2

Tank pressure on the wrist removes one instrument from your console and lets the computer calculate remaining gas time properly rather than estimating from depth alone. The bigger win with SubWave is seeing your buddy's pressure without asking, which quietly ends the most common underwater conversation there is.

Mapping and dive site data

Preloaded dive site data and surface GPS mean you can mark an entry point, find it again, and log where you actually were rather than where the boat said you were. For shore diving in unfamiliar places this is more useful than it sounds.

Battery that survives a dive week

The 51mm case carries a bigger battery and a bigger screen. On a liveaboard doing four dives a day, that difference decides whether you charge mid-week or not. If you are travelling light and charging nightly anyway, the 43mm is the more comfortable watch.

Sizes and compatibility

The 43mm suits smaller wrists and anyone who wants the watch to disappear under a cuff. The 51mm gives a larger, easier-to-read display and longer battery life, and it is the one most drysuit divers end up preferring because it is readable through a flooded mask at arm's length.

Both take standard Garmin quick-fit straps, so you can run a fabric strap daily and a longer silicone or bungee strap for diving. If you dive dry, budget for the longer strap. The stock strap will not close over a drysuit seal on most wrists.

We wrote up how the Mk3i compares against the rest of the watch-style field in our Descent Mk3i review, including where it loses to a dedicated technical computer.

Specifications

What's included

• Garmin Descent Mk3i in your chosen size and colour
• Fitted strap
• Charging and data cable
• Documentation
• Descent T2 transceiver only if you select a transmitter option above

Buying the Mk3i

This is the most capable watch-style dive computer we sell, and for divers who want one device for everything it is the obvious answer. It is not the cheapest way to get a reliable computer on your wrist, and if you only dive twice a year it is more watch than you need.

Where it earns the money is in the combination: air integration, buddy communication, mixed gas, and a watch you will actually wear on Monday morning. Get the case size and the transmitter decision right and it will be the last computer you buy for a long time.