Hi. Having used a 735XT for a few years I recently swapped to an Instinct. I am finding the open water swim general accuracy to be poor.
the read out is spikey with multiple max and min pace recordings as if the software struggles to compute the rapid gaining and losing of signal. The 735 appeared to take a more smoothed average.
is this just an no fitness specific watch issue? I thought it would use the same logic? And/or have I missed an update to fix it?
thank you. . 
is this just an no fitness specific watch issue?
I do not know, but I checked my OW swims done with the Instinct, and at almost all of them (regardless the firmware version) the pace is pretty smooth. Except of some short gaps, where I probably paused for a while, or did some strokes under water:
I use Every Second recording mode in the global system settings, and GPS+Galileo in the OW Swim settings.
... this is the same swim, with the graph in the zoomed version, so the small spikes of pace are better visible. Still, I think it pretty much respects the reality:
My 735 still gave me a much smoother output!
Could you post graphs from both devices, from similar swims, side by side? It would be interesting to know whether it is not just because of the graph scale. BTW, where does your graph come from? It looks neither like the one in Garmin Connect Web, nor like from the Garmin Connect Mobile app.
This is how the same swim from my previous posts looks like in Garmin Connect Mobile. Note the difference in the Y scale - at GCW it is from 30 min/100m to 0, while at GCM much narrower, from ~3:20 to ~1:40 min/100m. In your graph it is even narrower.
The spikes may be caused by GPS errors, but it can also fit the reality. This was an open water swim in a choppy water, so it would not surprise me at all, if each stroke did not take me to exactly the same distance from the other.
The difference between your two devices could be also caused by the difference in recording. If you could share links to two comparable OW swims, each with one of the devices, I could check the background data, to see the frequency of track points. What recording mode do you use on each device? The default Smart Recording, or the Every Second recording mode?
