Is this something that changed today? My swim workout from Wednesday (Lap Swim in 25yd pool) came out just like normal. Are you sure that you didn't select Open Water Swim when you started your activity?
In GC2 it shows yards/meters in the details and miles in the summary (list) view and if it is in the main activity widget thingie (recent activity, I think they are calling it). I just checked and it is displaying as expected in GC1 (yards/meters in Activities view) so I guess I am finding the GC2 views to be frustrating.