National Geographic : 1988 Jan
the adults swim offshore to graze the bottom, diving as deep as 12 meters (40 feet) for as long as 30 minutes. As an experiment, a sailor on the Bea gle sank an iguana with a heavy weight, and it was still alive an hour later. Darwin repeat edly threw one recalcitrant iguana into the sea and was puzzled when it quickly returned to shore, since he had been vividly impressed by its diving and swimming abilities. He must have picked a cold iguana; during their dives they can lose about 20°C (30 0 F) of body temperature.