Build a submarine - Fun at-home activities for Kids.

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Build a submarine

Build a small model submarine from a plastic bottle, clay, straws, and a weight to test buoyancy and control sinking and floating safely.

Table of contents

Step-by-step guide to build a model submarine

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How to Make a Submarine at Home Out of Plastic Bottle - Very Simple

What you need

Plastic bottle (empty), modeling clay, plastic straws, small weights (washers or coins), waterproof tape, scissors, basin or tub filled with water, decoration materials (stickers or markers), adult supervision required

Step 1

Gather all your materials on a clean table so everything is ready to use.

Step 2

Rinse and dry the plastic bottle to remove any drink residue.

Step 3

Remove the bottle label so you can see inside and decorate later.

Step 4

Ask an adult to carefully use scissors to make a small hole in the bottle cap just big enough for a straw to fit through.

Step 5

Push a straw through the hole so the straw tip reaches near the bottom inside the bottle and the straw top sticks out above the cap.

Step 6

Press modeling clay around the straw on the outside of the cap to make an airtight seal so no air leaks around the straw.

Step 7

Attach small weights to the outside bottom of the bottle with tape or clay until the bottle sits low in your hand but still floats when gently placed in water.

Step 8

Decorate the bottle with stickers or markers to make your submarine look awesome.

Step 9

Fill a basin or tub with water to use as your testing pool.

Step 10

Place your sealed submarine gently on the water with the straw top above the water surface and watch it float.

Step 11

Submerge the straw top below the water surface so water can travel down the straw and fill the bottle to make the submarine sink.

Step 12

Pull the straw top above the water and blow gently into the straw so air pushes water out and the submarine rises again.

Step 13

Add or remove small weights as needed to get the submarine to sink and float just the way you want.

Step 14

Repeat sinking and floating tests until your submarine moves smoothly and you can control it with the straw.

Step 15

Share a photo or video of your finished submarine and what you learned on DIY.org

Help!?

What can I use instead of modeling clay or a drinking straw if I can't find them?

Use hot-melt glue or silicone sealant in place of modeling clay to make an airtight seal around the cap, and replace a drinking straw with a piece of clear plastic tubing or a cut plastic pen barrel pushed through the cap so the straw tip still reaches near the bottom of the bottle.

My submarine leaks or won't float correctly—what should I check or fix?

If water leaks or it won't float, re-press or add more modeling clay around the straw on the outside of the cap to make an airtight seal, wrap tape around the straw if the hole is too big, and change the small weights attached to the outside bottom until the bottle sits low in your hand but still floats when gently placed in water.

How can I adapt this activity for different age groups?

For younger children have an adult pre-pierce the cap and pre-cut the straw and let them decorate and tape weights to the outside, while older kids can make their own airtight clay seals, test different bottle sizes, and fine-tune the amount of weights to control sinking and floating during repeated tests.

What are simple ways to extend or personalize the submarine project?

To extend the project add or remove small weights to experiment with buoyancy, glue on a small plastic periscope or a waterproof LED to the bottle for decoration, or attach a thin fishing line to guide the submarine while you practice submerging the straw to sink and blowing to rise.

Watch videos on how to build a model submarine

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Here at SafeTube, we're on a mission to create a safer and more delightful internet. 😊

Build a Submarine - STEM activity

4 Videos

Facts about buoyancy and water science

🛥️ Real submarines change depth by filling and emptying ballast tanks—your bottle sub does the same with water, air, and a weight.

⚖️ Archimedes' principle says an object floats when it displaces water equal to its own weight—perfect to test with a mini submarine.

🌊 Small tweaks (a bit of clay or a trapped bubble of air) can turn a floating model into one that hovers or sinks—tiny changes matter!

♻️ A recycled plastic bottle makes a great watertight hull—repurposing bottles is a super-easy way to build model boats and subs.

🧪 Straws can act as simple pumps or snorkels to trap or release air—kids can safely experiment with how air affects buoyancy.

How do I build a small model submarine from a plastic bottle to test buoyancy safely?

Start by cleaning a small plastic bottle and removing labels. Seal one end with modeling clay to create a ballast chamber; leave a removable clay plug to adjust weight. Attach straws for a periscope or ballast tube and tape securely. Add small weights (washers or coins) inside or attach clay to the outside to control sinking. Test in a tub, slowly adding or removing weight until the submarine floats neutrally. Always supervise water tests and adjust seals to avoid leaks.

What materials do I need to build a bottle submarine and test sinking/floating?

You'll need: one clean empty plastic bottle (1L or smaller), modeling clay or playdough, several straws, small weights (washers, coins or fishing sinkers), waterproof tape, scissors or an adult to cut, markers or stickers to decorate, a shallow tub or bucket of water, and a towel. Optional: hot glue (adult use), rubber bands, and a ruler for measuring sinking depth. Choose non-toxic materials and keep small parts away from young children.

What ages is this plastic bottle submarine activity suitable for?

This activity suits ages 5–12. Younger children (5–7) enjoy decorating and watching tests with close adult help for cutting, handling small weights, and sealing the bottle. Ages 8–12 can plan ballast placement, measure how much weight makes the model sink, and try adjustable designs. For toddlers, use a simplified floating bottle without small parts. Always supervise water play and keep small parts out of reach of children under 3.

What safety tips should I follow when testing a homemade bottle submarine?

Safety tips: Always supervise water play, keep small weights and clay away from children under three, and have adults handle cutting or hot glue. Test over a shallow tub to avoid spills and use non-toxic materials. Attach weights securely so they don't detach and become choking hazards. Rinse and dry the bottle between tests to prevent mold. For extra safety, avoid sharp metal sinkers—use coins or sealed washers instead.

Ready to create?

All Activities

Build a submarine

Build a small model submarine from a plastic bottle, clay, straws, and a weight to test buoyancy and control sinking and floating safely.

Table of contents

Step-by-step guide to build a model submarine

0:00/0:00

Here at SafeTube, we're on a mission to create a safer and more delightful internet. 😊

How to Make a Submarine at Home Out of Plastic Bottle - Very Simple

What you need

Step 1

Gather all your materials on a clean table so everything is ready to use.

Step 2

Rinse and dry the plastic bottle to remove any drink residue.

Step 3

Remove the bottle label so you can see inside and decorate later.

Step 4

Ask an adult to carefully use scissors to make a small hole in the bottle cap just big enough for a straw to fit through.

Step 5

Push a straw through the hole so the straw tip reaches near the bottom inside the bottle and the straw top sticks out above the cap.

Step 6

Press modeling clay around the straw on the outside of the cap to make an airtight seal so no air leaks around the straw.

Step 7

Attach small weights to the outside bottom of the bottle with tape or clay until the bottle sits low in your hand but still floats when gently placed in water.

Step 8

Decorate the bottle with stickers or markers to make your submarine look awesome.

Step 9

Fill a basin or tub with water to use as your testing pool.

Step 10

Place your sealed submarine gently on the water with the straw top above the water surface and watch it float.

Step 11

Submerge the straw top below the water surface so water can travel down the straw and fill the bottle to make the submarine sink.

Step 12

Pull the straw top above the water and blow gently into the straw so air pushes water out and the submarine rises again.

Step 13

Add or remove small weights as needed to get the submarine to sink and float just the way you want.

Step 14

Repeat sinking and floating tests until your submarine moves smoothly and you can control it with the straw.

Step 15

Share a photo or video of your finished submarine and what you learned on DIY.org

Help!?

What can I use instead of modeling clay or a drinking straw if I can't find them?

My submarine leaks or won't float correctly—what should I check or fix?

How can I adapt this activity for different age groups?

What are simple ways to extend or personalize the submarine project?

Watch videos on how to build a model submarine

0:00/0:00

Here at SafeTube, we're on a mission to create a safer and more delightful internet. 😊

Build a Submarine - STEM activity

4 Videos

Facts about buoyancy and water science

🛥️ Real submarines change depth by filling and emptying ballast tanks—your bottle sub does the same with water, air, and a weight.

⚖️ Archimedes' principle says an object floats when it displaces water equal to its own weight—perfect to test with a mini submarine.

🌊 Small tweaks (a bit of clay or a trapped bubble of air) can turn a floating model into one that hovers or sinks—tiny changes matter!

♻️ A recycled plastic bottle makes a great watertight hull—repurposing bottles is a super-easy way to build model boats and subs.

🧪 Straws can act as simple pumps or snorkels to trap or release air—kids can safely experiment with how air affects buoyancy.