Swim Distance Accuracy

May be it related to how Garmin calculate swim stroke:
"A stroke is counted every time your arm wearing the device completes a full cycle."
https://www8.garmin.com/manuals/webhelp/fenix5/EN-US/GUID-9481691E-B9E0-4793-BDF7-4F78D8703E2B.html
So it mean, that even if each of your arm take a swim stroke, Garmin counted only stroke by arm with weared watch.

LLRaven said:

May be it related to how Garmin calculate swim stroke:

Stroke count has no impact on calculated swim pace.

To my knowledge pool swim uses the compass to count one length. So if you turn or change style mid swim it will count an extra length each time.

The most important event that triggers length count is stopping arm movement for a while. And while indeed compass could be used to augment length count, there are garmin watches that do not have any compass, and yet they still count lengths as effectively as those with compass. More tips on how to improve length count accuracy can be found here:

https://support.garmin.com/en-US/?faq=iS2KcmGiVb4djrE1lri8i7

Accelerometer not compass for pool swimming. 

9674673 said:

I'm wondering how accurate the lap swimming distance and pace are

I've had few problems swimming in the pool with any Garmin watch I've owned. Lengths are detected pretty much 99.9% of the time even with the fumble turns or what ever else I do at the end of each length to change direction.

Distance is based on a multiple of the lengths detected times the distance set for the pool. As noted in the links provided a good stroke is needed for your watch to be able to detect you are swimming and determine when you turn at the end of the pool. If your lengths are counted accurately then pace is simply computed from the time taken and the number of lengths swum times the pool distance set.

Thank you. I have the pool length set accurately, so if the count is accurate (TBD on that, but it sounds like most people agree that it generally is) I'm going to be a very happy camper.