If you are using a external sensor with your device while on your activity go ahead and unpair and repair the sensor. That external sensor can play a part of how power is calculated, once done and the sensor is repaired please try the activity again to see if this corrects it.
Hi, I wasn't using any external sensor and my watch was in the water every other day for 1h as I swim frequently. Cleaning shouldn't be an issue. Elevation is also auto-calibrated. As for power, I do note that with HRM it's more reasonable, but still very much spiky like the screenshot, so the watch probably intrinsically isn't measuring it right and it messes with the external sensor rather than the other way round.
This is likely caused by the prolonged exposure to water, especially if it is chlorinated water in a pool. I've reached out to you via email to gather additional information.
