Is the Garmin CIRQA accurate for heart rate on the wrist?

In this open-water swim test, the wrist-worn CIRQA under-read heart rate by roughly 20 to 30 bpm against Polar Sense, WHOOP MG and Apple Watch Ultra 3. Wrist optical sensors struggle in open water, and this early result is consistent with that pattern. Further testing will follow.

Which heart rate sensor does the Garmin CIRQA use?

The CIRQA uses Garmin’s Gen 4 optical sensor (Elevate) with skin temperature added, which this site labels 4.1. It reads heart rate, HRV, SpO2, respiration and skin temperature.

Is the CIRQA more accurate on the upper arm than the wrist?

Optical sensors are generally more accurate on the upper arm than the wrist because the arm moves less and offers steadier blood flow. The CIRQA supports upper arm wear with a dedicated band, and arm placement is the more reliable option for heart rate during hard efforts.