How animals move ...

In this activity you should use your knowledge of forces to explain how animals move!

Remember that it is normally the reaction force on the body of an animal which gives rise to the resultant force. To obtain a reaction force, an action force must be applied in the opposite direction. There must be a resultant force on the body to change the velocity of the body.

More reading....

Animal Locomotion

http://en.wikipedia.org/wiki/Animal_locomotion

Dolphins
 

http://news.nationalgeographic.com/news/2014/01/140115-bottlenose-dolphins-swimming-paradox-ocean-animals-science/

Snakes
 

http://animals.howstuffworks.com/snakes/snake3.htm

http://www.ucs.louisiana.edu/~brm2286/locomotn.htm

Penguins

http://www.livescience.com/41998-emperor-penguin-huddle-physics.html