I am not getting enough heart readings to produce a chart when swimming. Why?

Hi

Apple Watch Series 2 records your heart rate continuously when you record a Pool Swim or Open Water Swim using the built-in Workout app:

Work out with your Apple Watch - Apple Support

However, keep in mind that Apple advises that performance of the heart rate sensor can potentially be adversely affected by water:

Swimming

For the best performance from the heart rate sensor, be sure to wear your Apple Watch snugly, but not too tightly, during your workouts. Apple suggests tightening your Apple Watch band before workouts and loosening it again afterwards. Certain other factors can also affect performance of the sensor:

• Wearing your Apple Watch - Apple Support
• Your heart rate. What it means, and where on Apple Watch you’ll find it. - Apple Support
• Get the most accurate measurements using your Apple Watch - Apple Support

Thanks. The same happens to me. It’s not a matter of tightening the watch to the wrist cause the heart app measures the beats in real time during the workout. The point is that afterwards when you want to check the graph, you just can’t and the watch says that not enough measurements were made.com Thats no sense as I could check that those are made. Help please.