This is anecdotal but the same exact thing (albeit with an Apple Watch vs. Android) happened to me a few days ago- I had forgotten to turn on the watch's water mode before going in the water. After about like 5 minutes in the pool it started calling 911 for a medical emergency. My watch ended up calling 911 about 3 times (it probably tried to call them about 5 more times but I ended up taking it off in time to prevent those calls- since it wasn't responding to my inputs at all). I also got a call from the Sheriff's office a little bit later and had to sheepishly explain that my watch was spam calling 911.
Still unsure what happened with it exactly, but whatever was triggering it to do this seemed to not simply be due to water on the screen since it tried to call 911 again even when I put the watch back on hours later after it had dried. I have since power cycled it a few times and let it run out of battery and it hasn't tried getting me arrested for spoof calling 911 again, so that's promising.