Garmin
Forerunner 255 Series
Long battery; but wrist HR tracking is inconsistent.
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I have a Garmin MK3i (43mm) that also does everything you will ever need a fitness watch to do. I decided on getting a dive computer that did fitness watch stuff instead of a fitness watch that did dive watch stuff, cause, you know. I really like my MK3i, it is excellent underwater, and I cannot recommend it enough.
I have a Garmin Descent in the 42 mm and no AI (it wasn't available in the MK 2 in the 42mm version, I think in the MK 3 it is now) but it's only a bit thicker than the Forerunner 945 I had before. I wear it 95% of days and it does everything I want for diving and other activities.
Descent g2. I dive 30 or so times a year. The descent mark2/3 feature of tank pod didn’t appeal to me greatly to justify double the price. In hindsight I probably would have gone with the g1 for the battery life, at the moment I get 2/3 dive days. Or a week of general wear and activity tracking. I love the g2 though, great all round watch, all the features I need, the amoled screen has amazing visibility in and out of the water
I just got a Garmin Descent G2 and I really like it. I have tiny wrists and it’s yet not too much for every day and still seems very functional for diving (I’ll let you know Friday, which will be my first dive with it). I also use it for runs and gym workouts. My husband has an MK2s he’s been using for three years and he loves it.
Second the G2. Bought it this July. Been solid. Diving padel and football are the activities I use it for . Nice and clear in the water .
Garmin descent G2 does that. In pool setting the distance you need to input manually. During the session you can do STA as well
Garmin
Forerunner 255 Series
Long battery; but wrist HR tracking is inconsistent.

Garmin
Forerunner 955 Series
Best value, clear MIP screen; limited smartwatch features.

Garmin
Fenix 7 Series
Durable, multi-week battery, flashlight; high price, buggy software.
Garmin
Instinct 2 Series
Rugged, solar multi-week battery; bulky, small screen readability issues.

Garmin
Enduro 3
Multi-week solar battery, lightweight; but bulky form factor.

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Garmin - Enduro 3

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Garmin - Fenix 7 Series

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Garmin - Forerunner 255 Series

Ranked #1
Oura - Oura Ring Series