Classroom activity Kindergarten Engineering & Design

The Mossy Marsh Sponge Wall: Two Ways to Slow the Water

A 30-minute kindergarten tray activity where small groups test a sponge row against a block row to see which one slows the water running toward a paper town.

Grade: Kindergarten
Subject: Engineering & Design
Material: Classroom activity
Time: 30 min
Prep: Moderate prep
Materials: A baking tray or shallow plastic bin, 1 per group, A book or block to tilt one end of each tray, Kitchen sponges, 3 per group, cut to fit across the tray, Wooden or plastic blocks, 3 per group, the same length as the sponges, A cup of water, 1 per test, poured from the same measuring cup, Small paper houses or squares of paper towel to act as the town, Towels for drying trays between rounds, A bowl for squeezing out the sponges, 1 per group

Standards

K-2-ETS1-3 NGSS

Analyze data from tests of two objects designed to solve the same problem to compare the strengths and weaknesses of how each performs.

How this material aligns: Each group pours the same cup of water down the same tilted tray behind a sponge row and behind a block row, then compares how wet the paper town got, which is the two-design test comparison this expectation requires.

All materials for K-2-ETS1-3 →

K-2-ETS1-2 NGSS

Develop a simple sketch, drawing, or physical model to illustrate how the shape of an object helps it function as needed to solve a given problem.

How this material aligns: The tray of sponges is a physical model of a marsh, and lifting the row out and squeezing it over a bowl shows how the sponge's open, holey structure does a job the solid block row cannot, which is the model of how shape helps an object function that this expectation names.

All materials for K-2-ETS1-2 →

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This material is in the public domain (CC0) and may be copied, edited, and shared freely, without attribution. Updated 2026-07-23.

Objectives

Students will build two different walls across the same tilted tray.
Students will pour water behind each wall and watch where it goes.
Students will say which wall kept the paper town driest and why.

Vocabulary

Key words: marsh, soak, wall, compare

Teacher overview

This is a small-group tray activity for groups of three or four. The tilted tray is a hillside, the top end is where the rain lands, and the paper squares at the bottom are the make-believe town of Mossy Marsh. Groups build two walls across the middle of the same tray, one row of sponges and one row of blocks, and pour the same cup of water behind each.

The two rounds carry the idea between them. A marsh soaks water into itself and lets the rest through slowly, while a hard barrier holds nothing and sends water around its ends in a rush. Students see both behaviors in the same tray within a minute of each other, which is why the two rounds must use the same tray, the same tilt, and the same cup.

Set trays on towels, because water runs off the low end of the tray in both rounds.

Activity Directions

Before class, cut sponges so three of them lie end to end across the width of a tray, and gather blocks of about the same length. Prop one end of each tray on a book so the tray tilts.
Put students in groups of three or four. Give each group one tilted tray, three sponges, three blocks, and four paper squares for the town. Have them set the paper town in a row along the low end of the tray.
Say the problem out loud together: rain runs down the hill toward the town, and the town keeps getting wet. Ask each group to point at the place where a wall should go, which is across the middle of the tray.
Round one. Groups lay the three sponges end to end across the middle of the tray. One student pours a cup of water slowly at the high end while the others watch the town. After the pour, everyone touches a paper square and says wet or dry.
Lift out the sponges and squeeze them into a bowl so students see how much water the sponge row was holding. Dry the tray and set out fresh paper squares.
Round two. Groups lay the three blocks end to end in the same place. Pour the same cup of water at the high end. Watch the water pile up behind the blocks and run around the ends. Touch a paper square again and say wet or dry.
Rotate the pouring job so a different student pours in each round, and stop the activity once every group has finished both rounds, roughly 20 minutes in.
Gather the class with one tray in the middle and work through the three debrief questions on the group page, taking answers from two or three different groups for each question.

The Mossy Marsh Sponge Wall: Two Ways to Slow the Water — Kindergarten Engineering & Design

Name: ____________________________ Date: ______________

Student Handout

Read each question aloud during the debrief. Groups answer together.

Which wall kept your paper town driest, the sponge row or the block row?
Where did the water go when it hit the block row?
A real marsh sits between a river and a town. What job does the marsh do?

From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.

Answer Key

Answer: The sponge row. Accept the row each group actually observed as driest, with a reason attached. In nearly every setup the sponges soak up a share of the water and slow the rest, so fewer paper squares get wet.
Answer: It piled up behind the blocks and ran around the ends. Blocks hold no water inside them, so once the water reaches the top or the side of the row it keeps going toward the town.
Answer: A marsh soaks up water and slows it down before it reaches the town. Accept any answer describing the marsh as holding, soaking, or slowing the water rather than blocking it completely.

Differentiation

Support (below grade level)

Assign these students the pouring job in round one and the touching job in round two so each has one clear task rather than several. Give them a two-picture card, a wet town and a dry town, to hold up as their answer instead of speaking during the debrief.

Extension (above grade level)

Ask these groups to run a third round with a wall that mixes sponges and blocks, predicting first whether it will act more like round one or round two. Have them explain to the class, using the word soak, why their mixed wall behaved the way it did.

ELL supports

Pre-teach soak, wet, dry, and wall by passing a dry sponge and a wet sponge around the circle and having the class say each word while squeezing. Accept pointing at the sponge row or the block row as a full answer to the first debrief question, and give every group the wet-town and dry-town picture cards described in Support.

Extensions

Take the class outside after a rain and look for a low, soggy spot on the school grounds where water sits instead of running off, then talk about what that spot does for the pavement below it. If your town has a rain garden or a wetland park, a short walk to look at the plants growing in the soggy soil connects the tray directly to a real place. Bring enough adults to supervise, and keep students on the path and away from open water.