avg open water swimming pace units.

What size of pool did you set in the options of the swim Activity? The units of the pool size are independent - you can set it to yards, even if metric system is selected in the general settings, so I suspect the wrong size of the pool may be the culprit.

25 meters pool size.

Ah, I just saw you meant Open Water Swimming so the pool size is irrelevant anyway. In that case reverify, what units are set on your device. It must be wrong, if the pace is shown in yards on the watch. You also did not tell what model you own, and where exactly you see the pace in yards - whether really on the watch, or rather in the GC Mobile phone app, or in Garmin Connect Web.

Garmin 5s plus.

I see it on GC app.

Its not in english, i know, but it says minute/yard.

OK, now post the screenshot of the screen GC Mobile Menu » Settings » User Settings, and especially the part with Measurment Units

It says metric