Step 1. At first you should create New layer. Settings you can see below:

Step 2. After that you can fill this layer with black color:

Step 3. Next you should create new layer:

Step 4. Now you should take Brushe tool and after that you can draw one white flexible line. With this line you can make experiments:

Step 5. Now you need to add some layer styles. Then you should go to Outer glow and select settings like this:

After that you should go to Inner glow and there you can select next settings:

Step 6. Now all that you draw in this layer can transform in to fire. For this you should draw crocodile.

Step 7. From this picture you should make crocodile brushe. You need go to Edit -> Define Brush Preset and after that you should named it crocodile:

Step 8. Now you have crocodile brush. You should open your fire layer and after that you can  draw your crocodile:

Step 9. Now you should duplicate layer with crocodile:


Step 10. After that you need to delete layers effects from duplicated layer. For this you should click on layer effects and pull them to trash:


Step 11. Now you should add blending mode to Overlay:

Step 12. Now you need to take Smudge tool and after that you can draw some lines under crocodile and then you should make crocodile teethes bigger. Below you can see the result: