Step 10: Use the triangle-like shape on the right side as a guide to draw the piranha's tail or caudal fin. Follow the basic path of the guides but make the shape more wavy as you darken the lines.
Step 11: Draw a small triangle-like shape on the top side of the body, to the left of the tail, for the piranha's adipose fin. Draw the anal fin under the body, to the left of the tail, using a series of lines. Follow the path of the body as you draw the outer edge of the fish's rectangular fin.
Step 12: Use the remaining lines and shapes as guides to draw the rest of the piranha's body. Simply darken the outer edge of the initial guide lines to create the shape of the body. Don't overlap the lines for the fish's fins as you draw the shape of the body.
Step 13: Draw a series of long, curved lines between the pectoral fin and eye for the piranha's gills. The first line should be the longest. Then add two shorter lines closer to the pectoral fin.
Step 14: For a cleaner look, erase as much as you can of the initial guide lines. Don't worry about erasing all of the guides. It's okay to leave some behind. Re-draw any final sketch lines you may have accidentally erased.
Final Step: Add some shading to your piranha drawing to give it more dimension and volume. Try to add the value evenly across the body for the smooth skin and avoid a rough, gritty texture. Shading can be time-consuming, so be patient and take breaks. Make a long section across the top part of the body a bit lighter to indicate shine.
Vary the pressure on your pencil to get different degrees of tonal value. Add a darker value across the middle, the lower edge and the near the fish's gills to emphasize the shadows and highlights. It's a good idea to use reference as you draw for an accurate piranha. To shade the fins, alternate between a light and dark value to emphasize the structure. Don't forget to pause the video after each step to draw at your own pace.