That's likely part of it. Unwitnessed cardiac arrests and those where no electrical activity is present in the heart are pretty rare to get back. Cold temperat

That's likely part of it. Unwitnessed cardiac arrests and those where no electrical activity is present in the heart are pretty rare to get back. Cold temperature and submersion in water are two neat caveats though. They can be viable a lot longer, in part due to the Diving reflex. https://en.wikipedia.org/wiki/Diving_reflex https://en.wikipedia.org/wiki/Diving_reflex