Time-wise, most websites are saying something like 15+ minutes.
I was involved in helping to rescue a kid once, and I lost all concept of time, and it felt a lot longer than it was. THAT kid drowned in a pond where the hospital I worked at just happened to be having its annual picnic, and that included EMTs who weren't on duty. He had no pulse when they started working on him, and it started and stopped a few times before they got him to the hospital. He made a full recovery. That was not too long after they discovered that you can't declare a person dead until they're warm and dead. Now, they induce hypothermia on purpose when they do bypass surgery.

This article says he's out of intensive care and his condition has been upgraded to "fair": masoncountydailynews.com/local-events/your-health/12335-boy-who-survived-drowning-meets-rescuer-condition-upgraded