Recently, I came across some STEM activities by The Ardent Teacher. The “Designing Life Jackets for Babies” looked like a great activity for getting students to experiment and think critically about design. I adapted the activity so that we would use weighted plastic army men instead.
We posed the following challenge: Create a life jacket that will keep your army man face-up above the water with just a piece of foam and 2 small rubber bands.
Since the army men float easily on their won, we attached weights to them (nuts from the hardware store were $.05 each!) to make it more challenging to float.
Despite attaching these weights, the students quickly found out how to keep their army men afloat. Anticipating this, we put different spins on the challenge:
- Imagine that 2 army men must share one flotation device. How could you modify your flotation device so that both men could stay face-up above water?
- In the real world, engineers face challenges all the time. Sometimes, you don’t have as much material as you’d like to create a design. But engineers find a way to make their designs work! Now, with half of the material you start with, create a life vest to keep 1 (or 2 if you want to challenge yourself!) army man afloat.
- Imagine that your army man is parachuting out of the sky and will be landing in the water. With the materials given, design a flotation device such that when he’s dropped from 1 or 2 feet above the water, he is able to safely float to the surface and keep his head above the water.
These variations kept the students engaged and trying new things. Sometimes the army man floated face-down or barely stayed above water, and the students would try placing the foam on different areas of the army man to counter his weight and help him float upright.
To wind down, our students switched gears and worked with Little Bits and Rainbow Looms! 
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