@Manuele
Same thing happened. But it wasn’t with snorkeling, rather open water swimming. Even though I swam a couple hundred meters, the watch detected the distance as 0. After ending the activity, watch was unresponsive. I restarted it, went to swimming again; same thing. Only this time it wouldn’t turn on after shutting it down. I tried it all, different button combinations, placing it to charge… nothing. I’ve received a replacement watch from a retailer, and I’ll be honest, I’m afraid to turn on swimming again. I’m 100% sure that it’s a software issue, as water damage would be very obvious, in all other areas the watch is perfect. Odd that this is the case with a minority of people, as I’ve read on other threads.