I had the same problem. To fix it I used the opening technique described on this website and disconnected the button assembly from the motherboard as the watch was starting but before the watch went into the bootloader screen. This was to test whether or not it was the buttons that were at fault. As it turned out the watch started working perfectly and could perform all functions without the buttons being connected. So for me it was the case that the buttons were malfunctioning. These are also the component that is closest to the easiest point of ingress for the water which is the microphone hole or via the gap around the buttons themselves. I then powered down the watch using the settings menu and disconnected the battery and sensors using the method described by this site. I then removed the motherboard, as described by this site, and I removed the two black rubber covers that sit on the buttons on the motherboard. Although there was no noticeable water damage, I left the motherboard out for 24 hours in a nice well-ventilated area at about 25 degrees to dry off. I then cleaned the button surfaces and the male and female connections that connect the button assembly to the motherboard with isopropyl alcohol as suggested by the earlier post. I reconnected everything and tested it. At, this point I determined I had fixed the power button as I was able to see options scrolling at the top of the bootloader screen and I could select power off successfully. I repeated the procedure twice more focussing on the secondary button and I was finally able to get the watch to boot normally with the buttons selected. Everything now works fine, except the secondary button is still a little unpredictable. It is crazy that the button assembly causes the watch to be unusable if it is broken, as the watch can operate normally without buttons at all. The problem appears to be that when the button assembly breaks in this way it sends a constant on signal from one or both buttons which results in the bootloader being constantly loaded and then start being immediately selected. I would be great if mobvoi could sell the button assembly as a spare part given that it can cause a major problem to the watch operation and would be reasonably easy to replace.