Hi fellow f6 user, this post is just a finding I want to share with you. If pool HR doesn't matter, skip it.
You find attached a comparison pool swim recording with a left-sided f6 Pro connected to the HR-Swim chest-belt and a right-sided competitor device, type Vantage V, well applied btw, picking up the wrist pulse rate WPR by optical means.
Just did alternately 5 x 100m breaststroke and 5 x 100m forward crawling in a 25 m pool with a really slow speed.
There is a large difference, and the credible reading is coming from Garmin's HR-Swim f6 Pro.
#1 Speed was intentionally slow, no HR over, say, 130 bpm in my case is likely.
# 2 You nicely see the freestyle / breaststroke intervals , which are clearly separated.
# 3 WPR shows spikes and unclear instabilities.
So, although I do not have to present a golden standard reference for the recorded HR (PR) - the clear winner is applying a HR-Swim. My preference and my advice to fellow pool visitors.
I will add the comparison between an f6 X (Saphire) connected to HRM - Swim and the f6 Pro (WPR) once, my f6 X-S has arrived.
Best, Road (I know with the presented swimming speed I better stick to my name 
).
