Hello Steve,
Thanks for reaching out on the Apple Support Communities. From your message I understand that you're concerned the Apple Watch is not recording the calories burned correctly.
If this is accurate, take a look at the screenshot which is shown next to, "View splits and sets," in this article: Swim with your Apple Watch. In the example shown If the person had swam for 3 hours, like your screenshot shows, they would've burned around 4600 calories. Based upon those rough estimates, and the fact that the example has a slower pace, your Apple Watch appears to be reading correctly.
In the article above, under "Get better results," you'll find information on how the workouts are measured. It states: "Pool Swim: When you start a workout, be sure to accurately set the pool length to help your Apple Watch measure laps and distance. GPS isn't used during a Pool Swim, and water might prevent a heart-rate measurement, but calories, laps, and distance will still be tracked using the built-in accelerometer."
Have you selected any other swimming strokes to see if the information changes?
If there is no change, follow these steps:
1 - Power off Apple Watch
2 - Power off iPhone
3 - Power on iPhone
4 - Power on Apple Watch
Be sure you've waited for each step to complete before proceeding to the next one. If you haven’t restarted the devices before, here’s how:
How to restart your Apple Watch
Restart your iPhone
Once you’ve restarted both, see if there is any change. If there is not, check to see that both your Apple Watch and your iPhone are running the latest updates to their operating systems. You can do so with these steps:
Update your Apple Watch
Update your iPhone, iPad, or iPod touch
All the best.
