Apple watch series 4 no longer counting laps while swimming.

My Apple watch series 4, which I received this past Christmas, has been working well while swimming laps. Today, however, after starting the workout and the lap timer, I noticed it wasn't counting my laps. After swimming a quarter mile or so, I ended the workout and checked the watch. Laps were still showing zero, but the watch did count the overall distance swum. Not sure what's going on. Is there any way to fix this or reset the watch? Anyone else experience the same thing?