Descent Mk3i (51 mm)

The Mk3i is the top of Garmin's dive line and the only wrist computer that will send a text message to your buddy underwater. SubWave sonar carries short preset messages and a diver locator up to 30 m (98 ft), and the same network brings tank pressure back from a Descent T2 transceiver. In a group where everyone is on the Garmin system, you can see who is low on gas before they signal it.

The case is 200 m (656 ft) dive rated with a scratch-resistant sapphire lens and metal buttons that stay operable at full depth, which sounds obvious until you have tried to work a touchscreen in 5 mm gloves. The AMOLED display is a touchscreen, but every dive function has a button behind it.

The built-in LED flashlight with a strobe mode is the feature owners mention first. It is not a dive light and it will not light a wall for photography, but it is exactly enough to read a gauge, find a clip or make yourself visible to a boat on a night exit, and it is on your wrist rather than in a pocket.

Gas support runs the full range: single and multiple gas, nitrox, trimix, gauge, apnea, apnea hunt and closed-circuit rebreather. Battery is up to 66 hours in dive mode. The 51 mm case is genuinely large, and if that is a problem the same computer exists at 43 mm.