Answer by Rory Young:
In addition having relatively large lung size proportional to its body, ais cold blooded and can reduce its heart-rate down to one beat per minute at will.
Beingmeans that they have a lower metabolic rate and htherefore can go for longer periods without food and oxygen. Reducing the heart rate lowers the metabolic rate even further.
On a croc-capture exercise I took part in twenty years ago or so on the Lower Zambezi we thought a large female we had caught had died. There was literally no sign of life whatsoever. After lying "dead" for over an hour under a tree she suddenly began "growling"!