I'm a 3 days user of a new AW Ultra (which costs 1000€ in Italy!). After a couple of session in which I've tightened the strap in several measures, and made a lot of tests that heart rate for swimmers is a dream! I would say my AW 6 was better. This is ridiculos since my friend swimmers with a 200€ Garmin/Suunto/Polar are able and they've a detailed graph without any particular setting. Any idea on how to fix?