One note about swimming is that unlike both Suunto and Polar, Garmin doesn’t capture heart rate data via the optical HR sensor while underwater. Garmin says that’s because the data isn’t as reliable. Which frankly, is kinda true. Though, I’ve found it varies a lot person to person. That’s probably why Polar basically says ‘Good luck with that’ for their wrist-based optical HR sensors for swimming, but, at least they allow it.