Last week I lost my Apple Series 2 watch while on a 20 mile bike ride across the Golden Gate into the Headlands. Of course, I didn't realize it was gone until I returned. I wasn't Mountain Biking mind you, where plenty of branches to catch the watch/crashes are the norm. This was a road ride (fairly smooth streets).
What the root cause? 3rd party watch bands. There was no way in hell that I was going to pay additional hundreds of dollars for just a fancier looking band, when there are ones on Amazon for $20. With that said... each side of the non-apple bands have 2 exposed little screws. These screws are normally encapsulated in the Apple sport band's silicon coating. On aftermarket bands, these are free to work their way loose. As soon as one falls out, the hinge mechanism holding the band to the watch falls into two pieces, meaning... instant fall from your wrist.
In the 3 months that I've had my watch, this has happened twice! The first time, I was literally just lifting my hand towards my mouse at my desk, and it just fell off (Of course, this was right in front of my boss who isn't an Apple fan). So, I ditched that band, thought it was a one-off. I got another cool looking 3rd party band, and a month later...it too fell apart.
Luckily, and I mean luckily, an honest guy on his mountain bike found my watch on the side of the road, took it home, charged it, and found out how to get to the "Emergency ID" section of the lock screen. He found my wife's phone number, called her, and I now have my watch back. Unfortunately, I didn't want to tell her about it (It was a birthday present), and so this goon is now the proud owner of two Apple Watches. By the way, the "Find my Watch" feature is useless unless the person who finds your watch takes it to a trusted WiFi, i.e,. my own house. Without a trusted WiFi connection, it will never update itself as lost to the person who found it.
My advice, if you get an aftermarket band, put liquid threadlock in those screw holes. It's one thing to pick your watch up at your desk. It's another thing to lose it surfing. Waterproof watches don't do any good at the bottom of the ocean...
Not hating the watch mind you, it's a cool gadget. I love not having to bring my phone on my bike rides. I just turn on Strava, Pool Swim, or Outdoor Run and hit it. The round crown knob is great for adjusting volume on my bluetooth headphones while jogging. Super easy to update my music playlist too. Swapping out the bands is pretty awesome too. I'm hoping that the latest band I ordered holds together better (the band and watch section are all one piece).