Yes, and that's the other thing. To reliably distinguish between drowning and breath-holding, you need to wait (or have more context) This device (which has t

Yes, and that's the other thing. To reliably distinguish between drowning and breath-holding, you need to wait (or have more context) This device (which has to come out through a secret underwater hatch and propel itself amongst people) cannot be faster than a lifeguard who has spotted the questionable situation and put themselves close to it before making a decision.