I’ve had my Fenix 5 Sapphire for about a week now and wanted to share my experiences of using the watch with the HRM-Swim.

My previous fitness watch was a VioiactiveHR and before that a Tomtom Multisport Cardio both of which I used for recording swimming. I usually do about an hour of lengths, al usually Breaststroke. The VivoactiveHR was in use for a couple of years and seemed to give plausible measurements but the calorie it gave for a given swim seemed a little high, and I really wanted to improve the accuracy  by adding a HRM. This was not possible with the VivoactiveHR as the HRM-Swim was not compatible, even the more recent versions don’t play nice together.

I looked at several alternatives such as a dedicated swimming focused watch with the HRM-Swim and even at some alternative manufacturers such as Polar. I was looking in depth at the new Forerunner but ultimately decided to spend the extra and go for the Fenix 5 Sapphire.


Initial set-up and phone linking was a doddle and I quickly got used to the use of the buttons to navigate, set-up screens, watch face settings etc. Initially overall impressed.

I’ve then started using it in the pool. I started out in the same way I’ve always swam lengths of breaststroke in our local 25m pool, I kinda kept an eye on the watch’s distance measurement and quickly realised it wasn’t in any way accurate in the slightest. So I stopped and saved the swim it had done so far and started a completely new swim. The watch then did not recognise any laps swam, I did 4 laps and it missed all of them. Again I stopped and restarted with a fresh swim and did another 4 lengths and all were missed.


A swift reboot of the watch later and starting again it recorded a few laps but wasn’t in any way counting all of them. Disappointed I contacted Garmin support who proceeded to copy and paste a procedure to factory reset the unit. I had only had the watch for a few days by then so thought I had nothing to lose because the next place it was going was back to Amazon if it didn’t start working.


A factory reset and a bit of faffing about later it was ready. I had read somewhere that people have previously reported issues with the length accuracy if you modified the swimming screen setting in any way so I left well alone. The default length for the pool is 25m in any case so I didn’t need to make any changes.


This made no difference, the lap recording was still as appalling as before. I started to suspect my stroke was to blame, so I started to do some lengths with front crawl, hey presto, t started counting. Front crawl isn’t my thing so I quickly got tired and went back to breaststroke but I was amazed to see that the watch was then correctly counting lengths with front crawl. After about 20 minutes the watch stopped counting lengths but it gave me an insight as to the problem.


I stopped the watch with the activity button and saved the swim. I then started a fresh swim and did my first length as front crawl, the watch recorded this fine, after the first length I switched back to breaststroke and it continued to count the lengths accurately. Again after about 20 minutes it stopped counting lengths. At this point I hit the activity button and stopped the swim, but I didn’t save or discard the swim I just left it for a few seconds on the stop screen. I then hit the activity button and did a length of front crawl and resumed breaststroke after that. All was well in the world.


My observations are thus. I have set-up an alert on the watch every 25m so I get a vibration on the wrist on every length. The Fenix watch will not ‘notice’ the swim has started unless I do a length of front crawl as my first lap, after that I can do whatever I like.


On the first length the length count will occur about two thirds into the length. After that the watch will increment the length counter after the push and glide on the 3/4rd stroke initially then after I have completed a couple of lengths then increment occurs on the second stroke at the mid-point when my arms are at full extension to the side.


If the watch stops counting lengths then it will usually be preceded by the last length or two before it loses the ability to count but the watch counting a double length. At that point I hit the activity button and stay on the stop screen for a few seconds. Another press of the activity button resumes the swim and with a push and glide, three strokes later a buzz on the wrist signifies the count has resumed.


It is a little annoying that a £400+ specialist fitness watch could have this niggle. But I see from the firmware release notes in version 10 the accuracy of the length counter was ‘improved’. I therefore assume it has just been played about with and optimised for a particular stroke at the detriment to another.