CHARLES DARWIN: It is a hideous-looking creature of a dirty black color, stupid and sluggish in its movements. The usual length of a full grown one is about a yard, but there are some even four feet long. ... When in water this lizard swims with perfect ease and quickness, by a serpentine movement of its body and flattened tail, , the legs being motionless and closely collapsed on its sides. A seaman on board sank one with a heavy weight attached to it, thinking thus to kill it directly, but when, an hour afterwards, he drew up the line, it was quite active.
The nature of this lizard's food, as well as the structure of its tail and feet, and the fact of its having been seen voluntarily swimming out to sea, absolutely prove its aquatic habits, yet there is in this one strange anomaly, namely, that when frightened it will not enter the water.. Hence, it is easy to drive these lizards down to any little point overhanging the sea, where they will sooner allow a person to catch hold of their tails than jump into the water. They do not seem to have any notion of biting, but when much frightened they squirt a drop of fluid from each nostril. I threw one several times as far as I could into a deep pool left by the retiring tide; but it invariably returned in a direct line to the spot where I stood. It swam near the bottom with a very graceful and rapid movement, and occasionally aided itself over the uneven ground with its feet. As soon as it arrived near the edge, but still being under water, it tried to conceal itself in the tufts of seaweed or entered some crevice. I several times caught this same loizard by driving it down to a point, and though possessed of such perfect powers of diving and swimming, nothing would induce it to enter the water; and as often as I threw it in, it returned in the manner above described.