Crocodylian locomotory patterns can be broken down into two different categories: Aquatic and Terrestrial. Since crocodylians are semi-aquatic animals, they have adapted to both life on land and life in the water. Still there are some forms of locomotion that one really doesn't expect from a crocodile.
Terrestrial
Even though they have been described as slow moving and lumbering animals when on land, I have never looked at crocodylians that way. To me everything from their amazing gallops to the common belly crawl, has always looked majestic and graceful. Anyway let's get down to the meat of this shall we.
The belly crawl is the one that most people view crocodylians as moving. In the belly crawl the legs are splayed out to the sides and move about in an oar like fashion. This is normally done slowly and for a short distance (it's mainly used to get in the water). But crocodylians are also able to move fast in a belly crawl. In this process the animal both moves it's body sinuously and slightly up and down. The legs still move sideways, but in a more diagonal progression so that the body rises up and down as the animal moves. The faster the crocodylian goes, the more sinuous the movements. A fast moving crocodylian in a belly crawl has it's entire body thrashing from side
to side, which migh look ungainly at first, but when one sees the distance covered by it, this "ungainly" movement becomes quite fluid.
Now many scientists, when attempting to explain this belly crawl, refer to to the way that most reptiles move. They state that when a lizard moves with it's splayed limbs, it doesn't raise it's body that far off the ground and is usually stuck dragging it behind. This is only a half truth. Some of the shorter legged lizards such as lizards in the Anguid family have bodies that are real long, and legs that are real short. The effect of this is, of course, that they drag most of their bodies on the ground when walking. On the other hand, we have the more common longer legged lizards such as the varanids, which are able to not only carry their bodies off the ground, but also around two thirds of their tails too.
Turtles, with the exception of the fully aquatic variety, are all able to carry their bodies off the ground. And then of course we have snakes, but they sort of speak for themselves in that department.
At any rate the belly crawl is the most commonly seen in crocodylians, not so much for it's frequency of use, just that the times that we usually view these animals are when they are resting and sliding into the water. Below is an example:
Fig.1
Fig.2
