Step 6: Draw a couple of curved lines toward the left for the top part of the cartoon crocodile / alligator's mouth.
Step 7: Draw a long, sloping line for the first part of the bottom of the crocodile's open mouth. Curve the line back up and draw another sloping line for the second part.
Step 8: Now draw a series of small triangle-like shapes along the top of the mouth for the crocodile's teeth. Add teeth to the bottom too.
Step 9: If you have room in the bottom part of the mouth, draw two curved lines for the crocodile's tongue.
Step 10: Draw a long wavy line under the mouth for the crocodile's lower jaw. Sketch lightly at first. When you get the shape of the jaw right, darken the line.