You can pair your Polar OH1+ with your Marlin in Marlin app. You will then able to hear the heart rate measured by Polar OH1 in Marlin Bone Conduction while your swim.
1. Go to Device -> Polar OH1 to pair your Marlin with your Polar OH1+
2. Go to OPTIONS (both Pool Mode and Open Water Mode) -> Report Heart Rate to enable the heart rate reporting, average heart rate will be included in the audio reporting if enabled.
3. Go to TARGET PERFORMANCE (both Pool Mode and Open Water Mode) -> Heart Rate Zone to enable and define the real-time heart rate zone for reporting. If you enabled and defined the heart rate zone here. You will also hear your real-time heart rate as measured by your Polar OH1+ if it is out of the range defined. This feature can facilitate you to listen to your body condition while swim.
4. You can also review your heart rate in each lap in your workout history