Streamlined sharks asks students to investigate the relationship between shape and water resistance, answering the question ‘What is the best shape for a shark?’. Sharks haven’t evolved much for the past 100 million years. Is there a reason for this? This investigation will be followed by a discussion of what would make the ultimate coral animal with students tasked to ‘design’ their own. During this activity you will test out different shapes to see if you can find a more streamlined shape than a shark and consider why the shark hasn’t changed for 100 million years.

Activity steps

1. You are going to investigate the relationship between shape and speed. Fill your large plastic container with water and ensure it is in a safe, stable position.
2. Take two equally sized lumps of modelling clay. Mold the first lump into a shape that you think will move slowly through the water. Mold the second lump into a shape that you think will move quickly through the water.
3. Make a prediction as to how long you think it will take for each model to sink to the bottom.
4. Hold the first shape at the water’s surface.
5. Ask a partner to use a stopwatch or timer to time how long it takes for each shape to fall to the bottom of the plastic container.
6. Drop your model and record the time it takes to reach the bottom of the container.
7. Repeat with your second shape.
8. Now take a piece of modelling clay and mold into the shape of a shark.
9. Make a prediction as to how long you think it will take for the shark model to sink to the bottom.
10. Drop your shark model and record the time it takes to reach the bottom of the container.

Review

• How did what you observed compare with what your predicted?
• Why do you think some shapes move more quickly through the water than others?
• How have sharks adapted to move quickly through the water, and why?

More ideas

There are over 400 different species of sharks, why not try making models shaped like Hammerhead shark or the Basking shark and see how their shape affects their speed through water.

• A large, clear plastic container filled with water
• Modelling clay or sticky tac
• Timers or stop watches
• Paper towels

Shapes of sharks

Sharks typically have an elongated fusiform body shape, which means they are long and tapered at each end. This body shape reduces drag and makes them very streamlined. A streamlined shape moves quickly though water because it has lower friction drag against the water.