Of course, living sharks don't just remain stretched out straight, like a fish at a sea food shop. They wriggle! They bend and bow and arch. And their pectoral and caudal (tail) fins change position as they move. You can add the illusion of liveliness to your shark drawings by modifying the basic method you've already learned. Instead of starting with an oval, start with a sort-of 'bent' oval — a kind of bean-shape. For example, you can bend your 'bean' downward, as shown here. You can extend the lines on either the head or tail end in the same or different directions, as long as the result seems believable. Because sharks have two pectoral fins, you can increase the three-dimensional (3-D) quality of your drawings by showing part of the pectoral on the other side of the body.
Try bending your 'bean' upwards and extend the head and tail parts of your shark in a way that makes sense to you. What about the pectoral fins from this angle? If you were slightly behind a shark, its pectoral fins would seem to point slightly forward. Sharks also have two pelvic fins. What would they look like at this angle? Experiment a bit: what would it look like if the pelvic fins were lowered like the pectoral fins? Keep on experimenting. Eventually, you'll build up a good understanding of what 'works' and what just doesn't look 'right'.
Sharks don't live in an ecological vacuum. To make your sharks even more realistic and life-like, it often helps to give them a realistic habitat. Where does the kind of shark you're drawing usually live? If it is a tropical reef shark, such as the one shown here, try adding some coral at the bottom. Add some surface ripples and perhaps some fishes in the background. If you want, you could draw your shark eating a fish or some other suitable prey animal.
What about color? Is the shark species you're drawing grey or blue or greenish or brown? Can you best capture the metallic sheen of a shark or the silvery fluidity of the surface or the roughness of the coral with pencil crayons or watercolor paint? Experiment! The possibilities are limited only by your imagination. So get some more paper and try everything you can think of. It's not really play, it's like exercise for the mind. But if you have fun while you're at it, so much the better!