Amazfit T-Rex 3 (48 mm) / Samsung Galaxy Watch6 (40 mm)

There is also a night display mode.

The 44 mm model has a 1.5-inch, 480 × 480 display.

The 22 mm strap is a standard width and can be swapped.

10 ATM means withstanding the pressure of 100 metres of still water for up to 10 minutes. Breath-hold training and testing are downloaded through the Zepp app.

A full charge takes about 3 hours; a magnetic charging base is in the box but no USB-C cable. Low-temperature mode gives 28 hours with GPS on and 32 days with it off. The maximum GPS mode works only in hiking and climbing modes.

According to Samsung, an 8-minute quick charge adds about 8 hours of use; charging is WPC-based wireless.

Dual-band positioning receives two frequencies from the satellites to reduce drift from reflected signals among tall buildings and dense trees; it uses more battery. Automatic mode switches settings based on signal strength.

The watch offers an altitude assistant, storm alerts, compass, sunrise/sunset and tide information, and prompts for blood-oxygen readings at high altitude.

ECG and blood pressure work through the Samsung Health Monitor app only in markets where they are approved; blood pressure needs calibration with a cuff every four weeks. Body composition should not be used by people with implanted devices such as pacemakers or during pregnancy.

Wi-Fi is used to download software updates without the phone. The watch shows incoming calls but cannot take Bluetooth calls; quick reply works on Android only.

Chest straps, running/cycling power meters and cycling speed/cadence sensors can be paired; data can be exported to apps such as Strava, komoot and Apple Health.

5ATM means water resistance to 50 metres for up to 10 minutes; the watch is not suitable for diving or high-pressure water. IP68 covers 1.5 metres of fresh water for 30 minutes.

Some features, such as the camera controller and health measurements, need a Galaxy phone.