Step one:
First draw an arc, like a standing hook.
Step 2:
Then draw its nose and abdomen with arcs, but do not connect them with another arc.
Step 3:
Use two arcs to draw the tail, and connect another arc in the middle.
Step 4:
Add two semi-elliptical fins and an arc-shaped belly.
Step 5:
Then add the eyes and draw the arced fins on the back.
Step 6:
Finally, apply a nice color, and the dolphin is finished.