Amazfit T-Rex 3 (48 mm) / Samsung Galaxy Watch5 Pro 45 mm

There is also a night display mode.

Sapphire crystal resists scratches better than mineral and aluminosilicate glass; the raised bezel around the screen protects the glass from knocks.

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.

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.

Bioelectrical impedance analysis estimates values such as body fat and skeletal muscle; results are not for medical diagnosis.

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.

The D-Buckle band uses a folding clasp so the strap sits at the same point every time, in place of a standard pin buckle.

Samsung says the battery is 60% larger than the Galaxy Watch4’s.

Wear OS 3 and later do not work with iPhone. Blood pressure and ECG work only in markets supported by Samsung Health Monitor and with Galaxy phones.

Track Back follows the recorded path in reverse to help you return to the start.

5ATM covers surface water activities such as swimming, not diving or high-pressure water. MIL-STD-810H is a set of military test methods, not a guarantee of impact resistance.