My wife got me one for our anniversary, we mainly went on a trip which I'd much rather do than gifts, but I digress.
I have a Rip Curl SearchGPS that I've always used to track kite and surf sessions, just because I like all of the analytics and knowing exactly how long you are in the water/days per year, etc.
The Apple Watch basically just adds heart rate to that, and it's pretty insane how many calories you can burn in a surf session, especially when waves are decent and you are moving a lot. There's also (not shockingly enough) a pretty big gap between riding my small boards where it takes more effort to stabilze and more paddling than my longboard SUP.
It does show your HRR for surfing and other exercises. I don't think I'm dying, but it won't let me do a ECG because my resting heart rate sits at 45.
