How can I restore the blue distance ring on Apple Watch?

I often use my Apple Watch for swimming workouts. I've enjoyed the little blue ring in the upper right corner which indicates distance swam. Recently this blue distance ring has vanished on my swim workout display. What gives? It's much easier to glance at this during a swim workout than read the number indicating laps.

It would also be helpful for other workouts like running and cycling. Can I get this display back?

[Re-Titled by Moderator]