Build a Submarine STEM Activity for Kids

Table of Contents

1. Introduction
2. The Science Behind the Submarine
3. Materials You Will Need
4. Step-by-Step Instructions
5. Troubleshooting the Engineering Design Process
6. The Connection Between Cooking and Physics
7. Expanding the Activity: From the Ocean to the Stars
8. Why Hands-On STEM Matters for Families
9. Educational Mapping: Bringing the Submarine to the Classroom
10. Structuring the Activity for Groups
11. Making Learning Delicious
12. Conclusion
13. FAQ

Introduction

Watching a child’s eyes light up when they discover how the world works is one of the most rewarding parts of being a parent or educator. Whether it is during bath time or a trip to the local pool, questions about why things sink or float are bound to surface. These moments are perfect opportunities to turn curiosity into a hands-on learning experience that combines physics, engineering, and a splash of creativity.

In this guide, we will walk through a build a submarine STEM activity that transforms simple household items into a functional underwater vessel. We believe in the power of "edutainment"—the idea that complex subjects like buoyancy and propulsion are best taught through tangible, joyful adventures. At I'm the Chef Too!, we strive to make learning an interactive journey that happens right at your kitchen table or classroom desk.

This activity is designed to help children understand the invisible forces of water while building something they can actually test. By the end of this project, your young engineer will have a better grasp of how real-world submarines navigate the deep ocean and how they can apply the scientific method to their own backyard discoveries.

Quick Answer: To build a simple STEM submarine, use a plastic bottle as the hull and attach weighted objects like pennies to the bottom for stability. Create a propulsion system using a rubber band and a plastic propeller to push the submarine through the water. By adjusting the amount of water inside the bottle, children can explore the concepts of density and buoyancy as the vessel sinks, rises, or floats in the middle.

The Science Behind the Submarine

Before we start building, it is helpful to understand the "why" behind the project. Submarines are fascinating because they defy the simple logic of "heavy things sink." A massive steel submarine can float on the surface just as easily as it can dive thousands of feet below. This happens because of two primary scientific concepts: buoyancy and density.

Understanding Buoyancy and Displacement

Buoyancy is the upward force that a fluid exerts on an object placed in it. You can describe this to a child as an "invisible hand" in the water pushing upward against whatever is sitting on the surface. This force was first described by a scientist named Archimedes. He discovered that the upward buoyant force is equal to the weight of the water that the object moves out of the way, or displaces.

When we place our plastic bottle in a tub of water, it pushes some of that water aside. If the bottle is filled with air, it is much lighter than the water it displaced, so the "invisible hand" pushes it back to the top. This is called positive buoyancy. When we want the submarine to dive, we have to change its weight so it becomes heavier than the water it is displacing. For another kid-friendly explanation, explore this buoyancy experiment guide.

The Role of Density

Density refers to how much "stuff" is packed into a specific amount of space. A lead weight and a piece of foam might be the same size, but the lead weight is much denser because its molecules are packed tightly together. In our submarine project, we use water and air to change the overall density of our vessel.

Real submarines have special compartments called ballast tanks. When they want to stay on the surface, these tanks are filled with air. When it is time to dive, the submarine opens valves to let seawater into the tanks, making the submarine denser. To surface again, they use compressed air to "blow" the water out of the tanks.

Key Takeaway: Submarines move up and down by changing their density. By replacing air with water inside their ballast tanks, they become heavy enough to sink. By replacing water with air, they become light enough to float.

Materials You Will Need

One of the best parts of this build a submarine STEM activity is that it uses items you likely already have in your recycling bin or kitchen junk drawer. Using everyday materials helps children see that science is happening all around them, not just in a professional laboratory.

For the Submarine Hull and Ballast:

• Plastic Bottle: A small, 16-ounce water or soda bottle works best. Ensure it has a tight-fitting cap.
• Pennies or Washers: These act as weights to help the submarine sit upright in the water.
• Rubber Bands: You will need several—some for the propulsion system and some to hold the weights in place.
• Popsicle Stick or Plastic Ruler: This acts as a frame or "fin" to keep the submarine stable.
• Waterproof Tape or Hot Glue: This is for securing components. If using hot glue, ensure an adult handles the glue gun.

For the Propulsion System:

• Plastic Lid: A yogurt or margarine tub lid works perfectly for cutting out a propeller.
• Paper Clips: Two large, sturdy paper clips.
• Push Pin: Used for making small pilot holes in the plastic.

Testing Environment:

• Large Container: A bathtub, a deep plastic storage bin, or even a kitchen sink filled with water.

Step-by-Step Instructions

Building a submarine requires patience and a bit of "trial and error," which is the heart of the engineering design process. We encourage you to work through these steps together, allowing your child to take the lead on assembly while providing support with the trickier parts.

Step 1: Prepare the Ballast System

Weight the bottom of the bottle. Use rubber bands or waterproof tape to secure several pennies or metal washers to a popsicle stick. Then, attach that popsicle stick to the outside of the bottle along its length. This ensures the submarine has a "heavy" side that will always face downward, preventing it from rolling over in the water.

Step 2: Create the Rear Support

Make a hole in the bottom of the bottle. An adult should use a push pin or a heated metal tool to carefully poke a hole in the center of the bottom of the bottle. Straighten one paper clip slightly to form a long hook. Insert this paper clip through the hole so the hook is inside the bottle and the straight end is secured on the outside. This will be the anchor for your rubber band motor.

Step 3: Build the Propeller

Cut a propeller from the plastic lid. Draw a small "X" or a four-bladed shape on your plastic lid and cut it out with scissors. Make a small hole in the very center of the propeller. Using a second paper clip, thread it through the center of the bottle cap and then through the propeller. Bend the paper clip on the outside so it holds the propeller in place but still allows it to spin freely.

Step 4: Assemble the Motor

Attach the rubber bands. Reach inside the bottle (or use a long tool) to hook a chain of two or three rubber bands onto the hook at the bottom of the bottle. Pull the other end of the rubber band chain toward the mouth of the bottle and hook it onto the paper clip attached to the cap. Screw the cap on tight. You now have a "twisted rubber band motor."

Step 5: Test and Adjust

Wind it up and set it afloat. Turn the propeller repeatedly to twist the rubber bands inside. This stores potential energy. When you place the submarine in the water and let go, that energy turns into kinetic energy as the propeller spins. If the submarine sinks immediately, you may need fewer weights. If it floats too high, try adding a little water inside the bottle before closing the cap.

Bottom line: The goal is to reach "neutral buoyancy," where the submarine stays suspended in the middle of the water rather than bobbing on top or crashing to the bottom. This requires careful balancing of weight and air.

Troubleshooting the Engineering Design Process

It is rare for a submarine to work perfectly on the first try. In the world of STEM, we call this the "iteration" phase. If the propeller doesn't spin or the submarine flips upside down, don't worry! This is where the real learning happens. You can extend the investigation with more water STEM challenges.

If the submarine flips over: The center of gravity is too high. Ensure your weights (pennies) are at the absolute bottom of the bottle. If the popsicle stick is too long, it might be creating drag that tips the vessel.

If the propeller is stuck: Check the holes in the cap and the bottom of the bottle. If they are too small, the paper clip won't spin. You can also add a small plastic bead between the propeller and the cap to act as a "bearing," reducing friction.

If the submarine won't move forward: Check the angle of your propeller blades. If they are flat, they won't "catch" the water. Carefully bend the blades at a slight angle so they push the water behind the submarine as they spin. This demonstrates Newton's Third Law: for every action (water pushed back), there is an equal and opposite reaction (submarine pushed forward).

Myth: A heavier submarine is always better at diving. Fact: If a submarine is too heavy, it will sink to the bottom and stay there. To be a true submarine, it needs to be able to displace enough water to stay "hovering" at a specific depth.

The Connection Between Cooking and Physics

You might wonder why a cooking-focused educational expert is talking about submarines. The truth is, the kitchen is the ultimate laboratory for studying density and displacement. Whenever we measure ingredients or watch dough rise, we are witnessing the same physical principles that govern underwater travel.

At I'm the Chef Too!, we often use these concepts in our kits. For example, when making our Galaxy Donut Kit, children see how different ingredients have different weights and how they interact to create a delicious treat. Measuring out liquids requires an understanding of volume, which is exactly what displacement is all about.

When you are in the kitchen together, you can demonstrate density easily. Fill a glass with water and drop in a grape—it sinks. Now, stir in several spoonfuls of salt. As the water becomes denser with the dissolved salt, the grape will eventually float. This is a simple version of how a submarine manages its ballast. The more "stuff" (mass) you pack into a space (volume), the more buoyant force you need to stay afloat.

Expanding the Activity: From the Ocean to the Stars

Once your child has mastered the build a submarine STEM activity, you can expand their interest into other areas of science. Submarines explore the "inner space" of our oceans, but the physics they use are very similar to those used in "outer space." For more ocean-themed ideas, try these under-the-sea STEM activities.

Connecting to Astronomy

Just as submarines have to handle intense pressure from water, spacecraft must handle the vacuum of space. You can use our Galaxy Donut Kit as a follow-up activity to discuss how scientists use technology to explore environments where humans can't naturally survive. Comparing the darkness of the deep ocean to the vastness of the solar system is a great way to spark a conversation about exploration and discovery.

Connecting to Nature and Conservation

Submarines allow us to observe marine life without disturbing it. If your child is fascinated by the animals they might see from a submarine window, our Wild Turtle Whoopie Pies kit is a fantastic way to blend that interest with culinary arts. As you bake and decorate, you can talk about the sea creatures that live at different depths of the ocean—from the sunlit zone at the top to the midnight zone at the bottom.

Connecting to Chemistry

The way a submarine surfaces using compressed air can also be compared to chemical reactions that produce gas. Our Erupting Volcano Cakes kit teaches children about the pressure that builds up when gas is trapped—similar to the pressure used to blow water out of a submarine's ballast tanks to make it rise.

Why Hands-On STEM Matters for Families

In a world full of digital screens, hands-on activities like building a submarine offer a rare chance for families to connect in a meaningful way. When we work with our hands, we engage different parts of our brains than we do when we are passively watching a video.

Building confidence through creation. When a child builds a submarine and sees it actually move across the water, they gain a sense of agency. They realize that they can solve problems and create functional machines. This confidence often carries over into their schoolwork and other hobbies.

Developing fine motor skills. Cutting out propellers, threading paper clips, and winding up rubber bands are excellent ways to practice fine motor control. These are the same skills used in the kitchen for whisking, pouring, and decorating.

Encouraging screen-free play. Activities like this provide hours of entertainment that don't involve a tablet or television. The "play" doesn't end once the submarine is built; children can spend the whole afternoon testing different weight configurations or racing their vessels in the bathtub.

Key Takeaway: STEM activities are not just about learning facts; they are about developing a mindset of curiosity, resilience, and creative problem-solving that will serve children for a lifetime.

Educational Mapping: Bringing the Submarine to the Classroom

For educators and homeschoolers, the build a submarine STEM activity is a goldmine for meeting curriculum standards. It touches on several key areas of the Next Generation Science Standards (NGSS) and common math frameworks.

Physical Science Connections

• Forces and Motion: Students can observe how the strength of the rubber band (potential energy) affects the distance the submarine travels (work/energy).
• Structure and Properties of Matter: This is the perfect time to introduce the concept of atoms and molecules. Explain how water molecules are packed more tightly than air molecules, which is why water is denser.

Mathematics Connections

• Measurement and Data: Have students record how many times they wind the propeller and measure how far the submarine travels. You can create a simple graph to show the relationship between the two.
• Volume: Use measuring cups from the kitchen to determine exactly how much water needs to be inside the bottle to achieve neutral buoyancy. This makes abstract volume concepts feel very real.

Engineering Design

The "Build-Test-Improve" cycle is the cornerstone of engineering. Educators can ask students to document their "failures" just as much as their successes. Did the submarine leak? Did the propeller fall off? Asking "why did this happen?" and "how can we fix it?" is how we train the next generation of engineers.

Structuring the Activity for Groups

If you are leading this activity for a classroom or a homeschool co-op, a bit of preparation goes a long way. We recommend setting up "stations" to manage the mess and the materials.

1. The Design Station: Here, students draw their submarine plans and decide where their weights will go.
2. The Assembly Station: Provide pre-cut propellers or have adults available to help with the cutting and hole-punching to keep the line moving.
3. The Testing Station: A large clear tub is best so everyone can see the submarines underwater. Have towels on hand for the inevitable splashes!

For larger groups, you might consider our school and group programmes. We offer options that bring these types of blended STEM and arts experiences into the classroom, making it easier for teachers to provide high-quality "edutainment" without the stress of sourcing every individual ingredient or material.

Making Learning Delicious

At the heart of everything we do is the belief that learning should be an experience the whole family looks forward to. Whether you are building a submarine from a plastic bottle or baking a batch of themed treats, the goal is the same: to spark curiosity and create joyful memories.

We have found that when you combine a physical activity—like building—with a sensory experience—like cooking—the lessons stick. Children don't just remember that "density equals mass over volume"; they remember the afternoon they spent with you, laughing as they tried to get their bottle to stay perfectly still in the middle of the sink.

By integrating STEM, the arts, and food, we provide a holistic way for children to explore their world. Our monthly subscription, The Chef's Club, is designed to keep this momentum going. Each month, a new adventure arrives at your door, ready to turn your kitchen into a laboratory, a theater, or an art studio.

Conclusion

The build a submarine STEM activity is more than just a craft project. It is an entry point into the world of physics and engineering. By using simple materials and a little bit of imagination, you can help your child understand the complex forces that allow us to explore the deepest parts of our planet.

Remember that the process is more important than the final product. Every time the submarine sinks too fast or the rubber band snaps, your child is learning how to think like a scientist. They are learning that challenges are just puzzles waiting to be solved.

Bottom line: Hands-on STEM activities build the critical thinking skills children need for the future while providing the fun they crave today.

Are you ready to start your next adventure? Whether you choose to explore the depths of the ocean with a DIY submarine or dive into the science of baking with our one-time adventure kits, the most important thing is to start creating together. Grab a bottle, some pennies, and a rubber band, and see where the current takes you!

FAQ

What is the best type of bottle to use for a STEM submarine?

A smooth-sided, 16-ounce plastic water bottle is usually the best choice because it is easy to attach weights to and has a standard cap size. Avoid bottles with very thin, crinkly plastic, as they can collapse under the pressure of the rubber bands or leak more easily when holes are punched in them.

Why does my submarine keep floating on its side?

This usually happens because the weight (the ballast) is not heavy enough or is not centered at the bottom of the bottle. To fix this, ensure your pennies or washers are taped securely to the "belly" of the submarine. You can also try adding a second row of weights to lower the center of gravity even further.

Can I make the submarine dive and surface on command?

To make a submarine that can dive and surface without being opened, you can attach a long piece of flexible plastic tubing to a hole in the cap. By blowing air into the tube, you can push water out of the bottle to make it rise, and by sucking air out, you can let water back in to make it sink.

Is this activity safe for younger children?

This activity is great for children of all ages, but adults should handle the sharp tools and hot glue. Younger children (ages 5-7) will enjoy the testing and winding phase, while older children (ages 8-12) can take the lead on the engineering and troubleshooting aspects of the build.