Garmin has multiple styles of Heart Rate Monitors. The standard Heart Rate Monitor (Hard Strap) and thePremium Heart Rate Monitor (Soft Strap) are not designed to provide heart rate data in the water. This limitation is related to the inability to transmit the heart rate data through the water.
These Heart Rate Monitors are designed to withstand 30 meters of water pressure, they can be worn while swimming without causing them damage. Being worn on the chest, the Heart Rate Monitors do not repeatedly impact the surface of the water as wrist-worn devices do.
After exiting the water, the Garmin device will begin to record heart rate data.