As we saw on the documentary the cove, Dolphins can stop breathing whenever they want. They have to force themselves to breathe, even when they are asleep. The dolphins only sleep with half of the brain, the other half remains awake so the dolphin remembers to breathe. I was incredibly interested on this quality that most of the animals including human being we took it for granted, and I started looking for animals that can stop breathing. A human being can only get 4 minutes to be resuscitated if they stop breathing.
The Wood frog on the other hand can stop breathing for the whole Winter! Because of the sub-zero temperatures, they can partially freeze their tissues so their heart stop beating. When the weather gets wormer, their heart wakes up and they start to breathe again.
How do they do this? Before they hibernate they allow glucose and urea to build up in their vital cells and tissues, for example the brain. These components make the water on the cells harder to freeze. This is pretty amazing considering that these little frogs can freeze and then after 3 or 4 months they can reanimate themselves.