Are you ready to take the penny boat challenge? It’s a classic! Water, water everywhere! Design a simple tin foil boat, and see how many pennies it can hold before it sinks. How many pennies will it take to make your boat sink? Learn about simple physics while you test out your engineering skills. We love easy STEM projects for kids!


Explore Buoyancy With A Tin Foil Boat

Buoyancy is the fascinating principle of physics that allows objects to float in a fluid, and what better way to explore it than through a fun STEM challenge involving tin foil boats? In this activity, participants are tasked with designing and building a boat entirely out of tin foil that can float and hold the maximum weight possible without sinking.

By manipulating the shape, size, and distribution of mass in their boats, participants will experiment with buoyant forces and discover firsthand how different factors affect the ability of an object to float.

Through trial and error, critical thinking, and creativity, participants will not only gain a deeper understanding of buoyancy but also develop valuable problem-solving skills essential to the fields of science, technology, engineering, and mathematics. So, let the tin foil boat challenge begin, and let the waves of discovery and innovation carry us to new heights of understanding!

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Penny Boat Challenge

Your challenge is to build a boat that can hold the most pennies or small coins before it sinks.


  • Large bowl of water
  • Green food coloring (optional)
  • 30 plus pennies per boat
  • Aluminum foil

Set Up:

STEP 1: Add a drop of green or blue food coloring (optional) to your bowl and fill 3/4 with water.


STEP 2: Cut two 8″ squares of aluminum foil for each boat. Then form a small boat from the aluminum foil. Time for kids to use their engineering skills!


STEP 3:  As a comparison, put 15 pennies on the other square of tin foil (not the boat), and have the kids ball it up and place it in the water. What happens? It sinks!


STEP 4: Place your boat in the water and see if it floats. Reshape if it doesn’t! Then, slowly add the pennies one at a time. How many pennies can you count before it sinks?

STEP 5: Extend the challenge by rebuilding your boat to see if it can hold even more pennies. Can your boat hold 100 pennies?


How Do Boats Float?

Our penny boat STEM challenge is all about buoyancy, and buoyancy is how well something floats in water or another liquid. Have you seen our saltwater density experiment?

You may have noticed that you saw two different results when you used the same amount of pennies and the same size piece of foil. Both items weighed the same. There’s one big difference, size.

The ball of foil and pennies take up less room so there is not enough upward force pushing up on the ball to keep it afloat. However, the tinfoil boat you made takes up a greater surface area so it has more force pushing up on it!


More Fun Science With Pennies

Want to use your pennies for more science activities? Grab the Penny Pack for just $.99!

More Fun STEM Challenges

There are so many easy STEM activities that kids can do with just a few simple supplies.

Straw Boat Challenge – Design a boat made from nothing but straws and tape, and see how many items it can hold before it sinks.

Strong Spaghetti – Get out the pasta and test your spaghetti bridge designs. Which one will hold the most weight?

Paper Bridges – Similar to our strong spaghetti challenge. Design a paper bridge with folded paper. Which one will hold the most coins?

Paper Chain STEM Challenge – One of the simplest STEM challenges ever!

Egg Drop Challenge – Create your own designs to protect your egg from breaking when it is dropped from a height. 

Strong Paper – Experiment with folding paper in different ways to test its strength and learn what shapes make the strongest structures.

Marshmallow Toothpick Tower – Build the tallest tower using only marshmallows and toothpicks.

Spaghetti Marshmallow Tower – Build the tallest spaghetti tower that can hold the weight of a jumbo marshmallow.

Gumdrop Bridge – Build a bridge from gumdrops and toothpicks and see how much weight it can hold.

Cup Tower Challenge – Make the tallest tower you can with 100 paper cups.

Paper Clip Challenge – Grab a bunch of paper clips and make a chain. Are paper clips strong enough to hold weight?

What Is STEM For Kids?

So you might ask, what does STEM stand for? STEM stands for science, technology, engineering, and math. The most important thing you can take away from this is that STEM is for everyone!

Read more: What is STEM?

Yes, kids of all ages can work on STEM projects and enjoy STEM lessons.  STEM activities are great for group work, too!

STEM is everywhere! Just look around.  The simple fact that STEM surrounds us is why it’s essential for kids to be a part of, use, and understand STEM.

From the buildings you see in town, the bridges that connect places, the computers we use, the software programs that go with them, and the air we breathe, STEM is what makes it all possible.

Interested in STEM plus ART? Check out all our STEAM Activities!

Engineering is an important part of STEM. What is engineering in kindergarten and elementary?  Well, it’s putting together simple structures and other items, and in the process, learning about the science behind them. Essentially, it’s a whole lot of doing! 

Helpful STEM Resources To Get You Started

Here are a few resources that will help you introduce STEM more effectively to your kids or students and help you feel confident when presenting materials. You’ll find helpful free printables throughout.

Printable STEM Pack for Kids

80+ Doable Engineering Projects in one convenient pack!

  • Full instructions with sample images
  • Activity-specific instruction sheets
  • Data Collection Sheets
  • Questions for Reflection
  • Architecture Building Cards: Try the tallest tower challenge
  • Bridge Building Cards: Explore different types of bridges to build your own.
  • Paper Chain STEM Challenge: Who can make the longest chain? Great icebreaker or quick challenge!
  • 3 Little Pigs Architectural Pack: Design a house that won’t blow away!
  • Great marshmallow challenge: A classic challenge kids love!
  • Real-world STEM challenge lesson but don’t know where to start? Our easy-to-follow template shows the steps!
  • What’s the difference between a scientist and an engineer?
  • Crossword and word search with engineering vocabulary.
  • Engineering vocabulary cards
  • Design a one-of-a-kind invention and write about it with this 5-page activity!

Get started with STEM and engineering projects today with this fantastic resource that includes all the information you need to complete more than 50 activities that encourage STEM skills!