Garmin Swim 2 lets you monitor your heart rate underwater

As well as smartwatch skills

Garmin Instinct 2 Surf Edition 45mm Rugged GPS Smartwatch, Mavericks 010-02626-12

Garmin Swim 2 guide - Apps on Google Play

HRM-Swim™

Swim and train everywhere with the Garmin Swim 2 GPS swimming smartwatch. It now monitors your underwater heart rate on the wrist in the pool or open

Garmin Swim 2 GPS swim watch slate grey/silver

Garmin Swim™ 2

Garmin Swim 2, GPS Swimming Smartwatch for Pool and Open Water, Underwater Heart Rate, Records Distance, Pace, Stroke Count and Type, Slate Gray : Electronics

Garmin Swim 2 GPS Watch In-Depth Review

Garmin HRM-Swim Heart Rate Underwater Accessory — PlayBetter

Wearable technologies

Garmin Swim 2 GPS Swimming Smartwatch

Garmin Forerunner 255 review

Garmin Swim 2, GPS Swimming Smartwatch for Pool and Open Water, Underwater Heart Rate, Records Distance, Pace, Stroke Count and Type, White : Electronics