This is not a question, because I know I won’t get an answer. It is rather a conclusion after having used quite a few Garmin HRM Tri, Swim and one Pro strap lately. Their lifespan in water is no more than 2 months!! For some reason, they stop working, or, they still do the job for running and cycling, but not for swimming. I don’t know if anyone else has had similar issues, but within a year or so, I have changed 3 HRM Tri, 2 HRM Swim and one Pro. Since they are supposed to be used in water too, I just don’t get it, why Garmin even produces them? 
Anyway, they give 2 years warranty, so I still get a new one for free every 2 months, but this is not the way it should be. If you design products for triathletes, you should also remember that triathletes swim. I swim every day. I need a strap that can be more reliable than that.