The first step: first draw a curve somewhat like "3".
Step 2: Then draw its mouth with a curve.
Step 3: Below the mouth, draw the belly and the tail with a curve, and pay attention to the curvature changes.
Step 4: Then draw short lines on the head and the back and connect them with curved lines to form the dorsal fin.
Step 5: The stomach is drawn with large curved lines to form the belly, plus a little bit of small curved structure.
Step 6: Then the back and the side of the face are also drawn with square fins, plus a few small horizontal lines.
Step 7: Then draw broken lines on the dorsal fin as well as dots for its eyes.
Step 8: Finally, paint it with nice colors and the seahorse is finished.