Building a mini submarine

A few weeks ago at our Family Inventors Lab, our book for the day was Papa’s Mechanical Fish, a really well-written and enjoyable book that shares the adventures of a family where the father is an inventor, who is sometimes successful and sometimes not. He is inspired to make a mechanical fish, and after several failed attempts makes a submarine the whole family can ride in.

At class that day, our main tinkering activity was to make a water-tight mini submarine that would keep a little paper person dry inside for 20 seconds underwater. Our supplies included plastic easter eggs, miscellaneous plastic containers, and tools that would help to waterproof things (tape, plastic bags, silly putty, things to wrap objects in, etc.)

This activity did what we hope to do with all our activities… it adapts to various ages and it teaches kids to experiment and adapt their efforts till they succeed.

Our littlest kids (2 – 3 year olds) mostly just used this as a sensory tub. They played with whatever was floating in the water.

Some of the middle-sized kids (3 – 4 year olds) did things like  float an easter egg inside a plastic bowl boat or fill plastic Ziploc bags with water and float those.

Our next oldest (4 – 5) tested the other containers: water bottles, small food containers, and some travel-size toiletry bottles to see which would keep a paper person dry. Some would and some wouldn’t. They also tried wrapping the eggs in various things (paper, cloth napkins, plastic bags) to see if they would stay dry. All of those failed, except sealing the egg inside a ziploc.

The oldest kids (6 and 7) did the full tinkering activity with the easter eggs. Testing, diagnosing, hypothesizing, building a prototype,  testing again, and repeating till we got it right. We learned that plastic easter eggs leak water because they have holes in the ends. We tried taping the holes and sealing the gaps with play-dough or silly putty. But even after you seal the holes, there’s a gap around where the two halves come together, and the eggs still leak. (And play dough makes a big mess when it gets wet!)

We eventually discovered a working solution: seal the ends of the eggs with silly putty. Put the paper person in. Wrap a silly putty seal all around the gap where the two halves of the egg come together. Submerge it. Count to 30. Bring it out of the water, dry it off, open it up, and Voila! we had created an easter egg submarine.

This is a great activity to repeat at home during bath time. Just grab a wide variety of plastic containers with lids from your kitchen, tear up some paper from the recycling bin to be your “people” you’re trying to keep dry, and head for the bath tub. Your child will learn about sinking, floating, water-tight vs. leaking, and the  fact that bubbles coming up from your submarine is a bad sign… if air comes out, water will go in!

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6 thoughts on “Building a mini submarine

  1. It’s the simplest activities where the most learning happens. I love that you did this with children of different ages and can see how they all get something different out of it. Thanks for sharing. A photo would be great :-).

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