Garmin has just released a beta software update to their athlete fitness watches the forerunner 945 series. This update now allows underwater HRM tracking via the optical HR,  this is big news for swimmers in particular as other fitness watches in Garmin’s line-up that offer optical HRM do not track heart-rate while swimming or in open water applications.

How to enable Wrist-based Optical HRM on your forerunner 945

This will eventually just be a part of the system updates but if you want to try it out today you just need to go to this link to download the beta from Garmin. Follow the ‘Installation Instructions’ on the bottom of this page to install the beta software onto your device.

To enable this HRM while swimming you need to firstly open the menu, scroll to ‘Wrist Heart Rate’, enter that menu, scroll to ‘While Swimming’ and toggle to ‘On’.

How accurate is wrist-based optical HRM underwater?

Garmin seems to have determined that it will be ‘accurate enough’ by allowing this functionality on the watch. Typically, optical HRM isn’t as accurate when compared to a HRM chest strap. You can improve results though if you make sure to have the watch secured fairly tightly to your wrist. Operating underwater will mean that your results could vary significantly but should be able to give you a base line on your performance.

As always though, if you want extreme accuracy then our recommendation is the HRM swim strap from Garmin as it will give you the most accurate data. If you’re happy enough with being able to gauge how much effort you put into that swim then this new feature makes are easy to do.

Can I get underwater wrist-based optical HRM on any Garmin device with an optical HRM?

At this stage it’s only available on the forerunner 945 but that will likely change depending on the feedback Garmin receives on this beta release.