Swim

Garmin swim 2 is what I use, had the Garmin swim 1 before it

pretty happy with garmin - stroke detection is pretty meh but that only matters if you need it. otherwise doesnt seem to affect laps and therefore distance, would say its 95% accurate as long as you manually stop the set so it doesnt trigger at the wall when you are fumbling with your cap and goggles.

just leave it at the wall if you are not going to stop. flipturns tend to trigger the lap pretty well, a good hard push is even better. only do the lap button when you complete your set and going to be stopped at the walk for a rest.

Use a watch to track your swims. I can only speak on pool because that’s where I swim. I use a Garmin swim watch and track my workouts on a 25 yd swim. It automatically tracks your HR and pace. On some rare cases like kicking with a kickboard and alternating arms (butterfly), it doesn’t track my swim so I manually have to use my watch to track the “drills section”.

Typical bluetooth devices generally do not work underwater. I wear my Garmin watch for swim tracking and my Open Water swim (mp3) headphones.

The HRM swim/pro would be a great addition to the testing. As a long time garmin user I find that optical (wrist based) is useful for body metrics tracking but for true zone training I’ve defaulted to the HRM. I’m currently also running the polar verity sense in parallel with my chest strap to see how the numbers compare. Not sure what the software is that you are using, but DcRainmaker has build a piece of software that will allow you to compare different devices outputs and it’s pretty cheap.