Build a Fish

Suggested Materials: 

• Small things that float
• Small things that sink
• Things that attach – paper clips, tape, etc.
• Bowl or basin filled with water

The Challenge: Can you design a fish that doesn’t sink or float to the surface, but instead stays in the middle of the water column?

STEM Concepts: Many fish need to be able to move through the water without sinking all the way or floating to the surface – they have to maintain neutral buoyancy by balancing gravity (which pushes them downward) and water’s buoyant force (which pushes them upward). 

Extensions: Do some research. How do fish prevent themselves from sinking to the bottom of Lake Champlain?

THE ENGINEERING DESIGN PROCESS

Define the Challenge: Design a fish that stays underwater – it doesn’t sink to the bottom or rise to the surface.

Plan Your Design: What makes something sink or float? What materials could you use to design your fish?

Create a Prototype: Build your fish!

Test Your Creation: Does your fish float? Sink? Stay in the middle?

Improve Your Design: How can you change the density* of your fish? Could you find any materials that were already neutrally buoyant?

*Density = Mass / Volume. In this experiment, we can think of density as how heavy something is compared to its size. Even though they are the same size, a golf ball will sink but a ping pong ball will float. That’s because the golf ball has a higher density. In order to accomplish this challenge, your fish needs to have the same density as water!