Amazfit T-Rex 3 (48 mm) / Samsung Galaxy Watch7 44 mm Bluetooth

There is also a night display mode.

The 2000-nit peak helps readability in sunlight; using the always-on display shortens battery life.

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.

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.

This version has no cellular connection; calls and notifications come through the paired phone.

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.

A fast wireless charging puck is in the box, but no wall adapter.

The L5 band helps separate signals reflected by tall buildings and trees; dual-frequency mode can increase battery use.

Availability of ECG and blood pressure depends on country and paired phone; blood pressure measurement is not offered in the US.

Energy Score turns sleep, activity and heart data into a daily readiness score; AGEs Index is experimental and not for diagnosis.

5ATM describes water resistance suitable for surface swimming; it is not for diving or high-speed water sports.