You may have lost satellite connection during your surf.
Unfortunately this may occasionally happen when using satellites to track water sports. For better results try to keep your Rip Curl SearchGPS watch close to the surface of the water as much as possible.
For best results get your watch into the START SURFING screen for five minutes before you get in the water. This will give the watch a stronger satellite connection and reduce satellite dropout.
Your watch has a GPS signal indicator that will begin flashing to tell you when you have lost signal.
Another possible reason is low battery. Your SearchGPS watch will shut down GPS tracking and save your surf when it reaches 5% battery remaining.