From Creatures Wikia
They a peaceful race who will tend to take their anger out on machinery. While being able to breathe underwater, they don't have any tendency to go into it.
They mainly prefer seeds and fruit, but will sometimes eat critters. They also use critters to get rid of boredom.
The most unusual thing about the lung grendels is the fact they are able to fly (with an included agent).
They can be downloaded here.