Garmin 310 XT GPS watch. Used condition but it works like it is new. Faint scratch on the screen. Compatible with ANT+ sensors.

Multisport GPS for Land and Water GPS-enabled training device for multisport athletes

Tracks time, distance, pace and heart rate on land

Times your swim and estimates distance and average speed

Water resistant to 50 meters

20-hour battery life

Wirelessly transfers data to Garmin Connect for analysis and sharing

Finally, a GPS-enabled training device that isn't afraid of the water. The rugged Forerunner 310XT is the triathlete's indispensable training tool a GPS-enabled trainer that is water-resistant to 164 ft (50 m), tracks data in multiple sport modes and sends it wirelessly to your computer. This multisport device has up to 20 hours of battery life, tracks distance, pace and heart rate on land, and goes from wrist to bike in seconds.

https://www.garmin.com/en-US/p/27335#specs