Level 2+: Tide Pools Unit

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We’re so excited to dive into an exciting new biome this week with our Tide Pools Unit! We’ll get up close and personal with a variety of residents, including sea stars (starfish), urchins, anemones, and more, and we’ll start thinking like a marine biologist with several hands-on activities, ending with a sweet treat for some Tea + Poetry. Begin by printing our skills tracker here, and then get ready to make a splash!

Note: Occasionally we include project modifications (which can be useful for including younger siblings) and upgrades (for children ready for more). We’ll mark those with the minus (-) or plus (+) symbols.

What you need:

Books (find at your local library or order below on Amazon):

Optional additional books:

Supplies (use what you have, but here are links to shop if you need anything):

What to do:

We recommend doing the below lessons in this order to build on each skill your child will develop, but don’t feel that you *need* to do them in this order. Do what works for you and your child. If they love an activity, feel free to repeat! Not a winner? Skip and try the next thing. Have fun!

Phonics Guide:

New to our phonics guide? Start here. Our last three units in Level 2+ won’t be adding any additional rules or phonograms to your child’s Phonics Guide. Instead, use these weeks to regularly review their guides to help reinforce what they’ve learned! You may also wish to pull out activities you’ve done to help reinforce any rules they’re still struggling with.

Lesson 1:

A tide pool (also called a tidal pool, tide pond, or tidal pond) is an isolated pocket of seawater found in the ocean’s intertidal zone. Formed in depressions along the shoreline of rocky coasts, tide pools are filled with seawater that gets trapped as the tide recedes. While these small basins at the ocean’s edge typically range from mere inches to a few feet deep and a few feet across, they are packed with sturdy sea life such as snails, barnacles, mussels, anemones, urchins, sea stars, crustaceans, seaweed, and small fish. (source) The life found in these fascinating biomes must endure a variety of struggles, from pounding surf to increasingly hot temperatures when the tide recedes, which is why some of the creatures you’ll find have some especially interesting characteristics! Let’s get an overview of what you might see in a tide pool with our first books for the week. You can read At Home in the Tide Pool (or read it here on OpenLibrary) OR In One Tidepool: Crabs, Snails, and Salty Tails (or read it here on OpenLibrary) OR The Tide Pool Waits, or any tide pool book you were able to find at your local library.

Activity 1: So what is the intertidal biome? Let’s learn more about it in this video. The video also shares more about what causes the tides. The moon’s gravitational pull on the Earth and the Earth’s rotational force are the two main factors that cause high and low tides. The side of the Earth closest to the Moon experiences the Moon’s pull the strongest, and this causes the seas to rise, creating high tides. On the side facing away from the Moon, the rotational force of the Earth is stronger than the Moon’s gravitational pull. The rotational force causes water to pile up as the water tries to resist that force, so high tides form on this side, too. Elsewhere on the Earth, the ocean recedes, producing low tides. The gravitational attraction of the Sun also plays a small role in the formation of tides. Tides move around the Earth as bulges in the ocean. (source)

Next, do this activity with your child to demonstrate how the tides affect the lives of animals and plants in this dynamic biome.

Activity 2: Not all tide pools are the same―and just like the ocean or caves, they have different zones with different conditions and different types of life. Tide pool habitats can be divided into four major zones, the splash (or spray) zone, high zone, middle zone, and low zone; the splash zone tends to be only rarely covered by water while the low zone is only exposed to air during extreme low tides. (source) This video breaks down the different zones and what you find in each of them.

The splash or spray tidal zone is dampened by ocean spray and high waves and is submerged only during very high tides or severe storms. The few animals that can survive here include fungi and algae, isopods and periwinkles.

The high intertidal zone floods during the peaks of daily high tides but remains dry for long stretches between high tides. It is inhabited by hardy sea life that can withstand pounding waves, such as barnacles, marine snails, mussels, limpets, shore crabs, and hermit crabs. (source)

The middle intertidal zone, over which the tides ebb and flow twice a day, and which is inhabited by a greater variety of both plants and animals, including sea stars and anemones. Organisms in this area include anemones, barnacles, chitons, crabs, green algae, isopods, limpets, mussels, sea lettuce, sea palms, sea stars, snails, sponges, and whelks. Rock pools that contain water can also provide a habitat for small fish, shrimps, krill, sea urchins and plankton. )

The low intertidal zone is virtually always underwater except during the lowest of spring tides. Life is more abundant there because of the protection provided by the water. Animals include anemones, seaweed, chitons, crabs, green algae, hydroids, isopods, limpets, mussels, nudibranchs, sea horses, fish, sea cucumber, sea lettuce, sea palms, sea stars, sea urchins, shrimp, snails, sponges, surf grass, tube worms, and whelks. (source

Next, let’s create this project to sort the types of life you find in each zone. First, print these creatures found in each of the zones and let your child color them in. Cut them out (you may wish to cut out the labels with each animal to help identify them).

Next, take a piece of yellow or light brown cardstock to represent our sand/splash zone. To create the other zones, layer and glue down three sheets of light blue tissue paper, creating progressively darker layers down the cardstock. Label each zone with a black marker or pen. It should look like this:

Finally, sort and glue the plants and animals into the correct zone. For animals that can exist in multiple zones, you may wish to glue them along the line differentiating the zones.

Activity 3: One of the most unsung heroes of the tide pool is the mussel. Mussels help to keep the water in tide pools clean by filtering out impurities and debris.

Mussel beds, found in most tide pools, are one of the most important biological habitats because of the diversity of organisms. Barnacles, snails, limpets, worms, and insects are found in large numbers inside mussel beds. Because of their importance, scientists monitor the health of mussel beds along the coast. The size of the bed and the changes in density of the mussels over time provide scientists with information to assess changes to a wide variety of plants and animals which depend on the mussel beds.

Because mussel beds are so large, however, it is not possible to count the exact number of mussels in each bed. Instead, scientists rely on estimates based on collecting repeated samples. Here’s how they do it: Scientists with take a rectangular photo of a block of the mussel bed that they keep marked with permanent bolts. Each time the scientists return, they are able to locate the bold and take photos in the exact same location.

Scientists then take the digital photos back to the lab and reproduce them on a computer screen. A series of points is overlaid and the species under each point is identified. This measurement will provide the scientist with the percent cover of mussels for that plot. The mussels in each plot are counted and recorded either directly in the field, or using a photo of the plot. An estimate of the total number of mussels at a site can be made by multiplying the number of mussels counted in the plots required to cover the mussel beds at an entire site.

For today’s math activity, we’ll practice thinking like a marine biologist while exercising our estimating and multiplying skills.

Begin by printing this photo of a mussel bed. Ignoring the grid for now, ask your child how they think a scientist could determine how many mussels are in the bed. (For example, they could count each one…but how long would that take?) Ask your child to estimate how many mussels are in the whole photo and write this number on the bottom or back of the sheet or on a separate piece of paper.

How can we verify this number without having to count every single mussel? This is where scientists use math to find answers! Have your child select one rectangle, or plot of the grid. First, have them estimate how many mussels are in that plot. Write down this number as well. Now, count the number of mussels in that plot. Write down the actual number. How close was your estimation? What are the pros and cons of estimating over counting?

Now, let’s use some multiplication to determine how many mussels are likely in the entire bed. Using your actual number from the plot, multiple it by 12. This answer gives you a pretty good idea of how many mussels are in the whole section.

Pretend this photo represents one tenth of the entire mussel bed. To find the total number of mussels in our “bed,” multiply your answer by 10.

How does this method save scientists time and effort when monitoring the life in a mussel bed?

Lesson 2:

Today, we’ll be focusing on a favorite creature found in tide pools: the starfish (or, as it’s more commonly known in scientific circles, the sea star)! Begin by reading the book Star of the Sea: A Day in the Life of a Starfish (or read it here on OpenLibrary).

Here are some other fun facts your child might like to know about sea stars:

  • There are around 2,000 species of sea stars
  • They can regrow an arm (ray) if they lose one
  • They do not have blood
  • Most have only five rays, others can have many more arms
  • They only live in salt water
  • They come in a variety of colors
  • Starfish are carnivorous
  • Sea stars only see light or dark
  • They are not fish; more closely related to sea urchins and sand dollars (source)

Activity 1: Begin by making your own sea star with this craft. You may want to get inspiration for your sea star’s colors and patterns from this video.

Activity 2: Most sea stars have five arms, although some can grow as many as 50 arms!! (source) For our next activity, we’ll be focusing on the majority as we practice multiplying by fives. You’ll need these sea star figurines, or you can print page 1 of this printable and cut out the sea stars. If skip counting is new to your child begin by having your child count the arms on one of the sea stars, and then practice skip counting by fives as you count each sea star.

Next, remind your child how multiplication is a faster way of skip counting. On a separate piece of paper, demonstrate how they could take 3 sea stars and count their legs individually (1, 2, 3, 4, 5, 6, etc.), skip count by fives (5, 10, 15), or they could take 5 x 3 = 15.

If they enjoy working with math sheets, print the second page of the printable to practice the 5 times tables.

We also recommend printing this multiplication chart to keep handy as a visual reminder until your child has memorized multiplication tables.

Activity 3: The reason why scientists prefer the term “sea star” to “starfish” is because sea stars are not fish at all―they are actually much more closely related to another create called the sand dollar.

Sand dollars are another super cool creature often found in and near tide pools. You can learn more about this in this article, or by watching this video.

Let’s let sand dollars inspire our next activity while we work on some sight words. Print 1-2 pages of these sand dollars on white cardstock or other thick paper. Cut out the sand dollars. On the back, create pairs of sight words that your child can practice for a memory game. (Click here for an example list of some sight words that your child might be ready to work on.) Alternately, you could put a unique word on each sand dollar and skip the memory game party.

Present the sand dollars to your child word side down, and let them flip to try to make matches. When they get a match, see if they can read the words. If they do, they can keep the pair. If not, they have to put them back in the “sand bed.”

Lesson 3:

One of the most recognizable members of the tide pool is the sea anemone! Let’s read a charming story about one with the book Anemone is Not the Enemy (or listen to this read aloud). (Note: The simple, conversational writing style of this book is great for young readers―your child may even be able to read it to you!)

Next, watch this video to learn more about how anemones stay alive.

Activity 1: Anemones capture prey and protect themselves by using stinging capsules called nematocysts. Nematocysts contain a harpoon-like spine that is fired into the tissue of prey or potential predators. A notable exception to these attacks, though, is the anemonefish (also called a clown fish), which actually live within the anemone. How does this fish maintain such close contact without getting stung?

The currently accepted explanation is that anemonefishes are not stung because they have a protective agent in the mucus that coats their bodies. The interesting question is how do anemonefishes build up this protective coating?

There are two current theories. One is that during several hours of ‘acclimatization’ swimming the fish smears mucus from the anemone onto its body. In the same way that the mucus prevents the anemone from stinging itself, it will likewise protect the anemonefish. The second theory is that the mucous coating of anemonefishes lacks the component that stimulates anemones to fire their nematocysts. (source)

Let’s do a quick hands-on activity to demonstrate how this protective coating might protect an anemonefish. You’ll need a piece of Velcro and a thick gel cream, like petroleum jelly.

Pretend the hooks of the Velcro are the spine of the anemone and have your child rub it along the skin of the top of their hand. It likely won’t really hurt, but it will feel very scratchy. You can imagine if there was an itchy irritant on the tops of those spines (or if they were sharper), it would easily cause a rash or other pain.

Next, spread a thick layer of the petroleum jelly on the back of their hand and repeat the activity. The effect of the hooks will be barely noticeable now. In the same way, the mucus coating on the anemonefish protects it from feeling the sting of the anemone.

Activity 2: Not only is the clown fish unharmed by the anemone, they actually have one of the most famous mutual symbiotic relationships in the animal world! We learned about symbiotic relationships in our Level 2: Savanna + Safari Unit, but let’s review the activity now (or do it for the first time if you haven’t done that unit!).

First, watch this video to learn more about symbiosis. There are actually different types of symbiosis in the animal world. Today, let’s learn about the three main types: mutualism, commensalism, and parasitism. Review the definitions of each below, and then complete our activity to bring it life in a hands-on way.

  • Mutualism: A symbiotic relationship where both sides benefit.
  • Commensalism: A symbiotic relationship where one side benefits and the other is unaffected.
  • Parasitism: A symbiotic relationship where one side benefits and the other side is harmed in some way.

Let’s bring it to life! Print this symbiosis activity and laminate, if possible. Cut out the relationship cards and creature circles. Using velcro dots, put one dot on the back of each of the creature circles (use the rough side of the velcro dot) and put a soft Velcro dot on the end of a popsicle stick. As you review each relationship cards, have your child attach the creature circle to the popsicle stick so it can “interact” with the plant or animal on the relationship card. Read them the details of the relationship and ask them to determine which type of symbiotic relationship this is. They can then sort the relationship card into the printed chart.

Activity 3: Next, make this craft of an anemone. (You could also print a picture of a clown fish or use a figurine to live within your anemone!)

Activity 4: Another animal often confused with the anemone is the sea urchin. We won’t have time to dedicate a full day to urchins this week, but let’s learn a bit about them now. Begin by watching this video to learn more about the sea urchin. Your child may also enjoy this time-lapse video of how a sea urchin moves!

Sea urchin spines are composed of calcium carbonate. In its basic state, this is a rather brittle mineral, but microscopic blocks of nacre (mother of pearl) help to strengthen it. (source) Even so, the spines to still break off from time to time. Fortunately, the urchin is able to regrow its spines within a day or two of them being broken. (source)

Let’s use the urchin’s spines to inspire a math game. (You may remember doing something similar in the Level 2: Forest Unit with the porcupine!) First, print this game board and tape it together.

Next, give your child a small lump of play dough to roll into a ball for the urchins body. Start them with 20 toothpicks to stick in for the spines. They will also need a separate piece of paper to track their spines throughout the game. (-) If playing with a younger child, just have them add and take away spines and then count their new total at the end.

Use a small stone for each player’s marker. Take turns rolling a die to move from rock to rock, adding and subtracting spines along the way. Have your child keep track of how many spines they have with each move using addition and subtraction. When you read the algae at the end (a favorite treat of urchins!), see who has the most spines remaining.

Lesson 4:

Moving along in our introduction of some of the most popular tidal pool creatures, we have the sea horse! The sea horse is typically found in the low intertidal zone, where there is almost always water and the currents are typically strong. Let’s learn more about this animal in the book Sea Horse: The Shyest Fish in the Sea (or read it here on OpenLibrary). You can also learn more about their lives in this video.

Activity 1: Let’s begin with a craft that will also help us identify the sea horse’s anatomy and get some handwriting practice. Begin by creating this sea horse on a piece of light blue or white cardstock.

Once it’s dry, use a thin black marker or pencil to label the following parts of the sea horse (or as many as your child is willing to write):

(source)

Activity 2: The sea horse also has one of the most interesting life cycles in the animal world because the males actually carry and gestate the young. To accomplish this, the female sea horse deposits the unfertilized eggs in the male’s brood pouch, where they are then fertilized. They babies then grow and develop in the pouch, which will appear extended much like any other pregnant belly. Once the babies are ready for life in the open sea, the pouch will open to release the baby sea horses―sometimes hundreds at a time!

Let’s bring this to life with a life cycle wheel craft! First, print these pictures that will illustrate the phases of the life cycle on a piece of white cardstock and let your child color them in. (The semi-circle will represent the sea horse’s extended belly, so they can color it a similar color to the larger male sea horse.)

Once the pieces are colored in, cut them out. Fasten the larger male seahorse to a paper plate using a brad through the curl of his tail and the middle of the plate. Glue the remaining pieces so they interact correctly with the male seahorse, like this:

Finally, label each stage of the life cycle. Now, you should be able to rotate the plate behind the male seahorse to demonstrate the cycle!

Activity 3: Ready for some Tea + Poetry? First, make these adorable Tide Pool Cookies. When they’re ready to eat, pull out Friends and Anemones: Ocean Poems for Children if you have it, or, if you own Sing a Song of Seasons, you can find many tide pool-themed poems in the August section of the book.

Lesson 5:

For our last day of activities, we’ll learn about a funny creature with some fascinating habits―the hermit crab! Begin with the classic book A House for Hermit Crab (or read it here on OpenLibrary).

Activity 1: The illustrations of this book are a great example of collage art, and the crab himself seems to be making an art piece of his shell. Let’s use that as inspiration for our own craft. First, use sponges and paint to decorate a thin paper plate. Once dry, cut the plate into a spiral and create this craft with your child’s photo. Finally, print real photos of the animals that the hermit crab attached to his shell from the internet, cut them out, and glue them onto your collaged shell to complete the piece. As your child works, use this as an opportunity to review the sequence of the story―this is a great way to see what your child retains as you read!

Activity 2: When a hermit crab outgrows his shell, he needs to find one that’s not too big or too small to move into. Let’s use that as inspiration for a measuring activity. Print these hermit crab and shell cards and cut them out. Have your child use a ruler to measure each crab (in case they ever wondered what a hermit crab looks like without their shell!) and shell, matching the ones that are the same width. Once they have made their pairs, have them put the pairs in order from smallest to largest.

Activity 3: Non-aquatic hermit crabs actually make great first pets for many children. If your family is looking for a new, low-maintenance pet, this article shares tips on how to best care for a pet hermit crab.

Activity 4: Let’s end our week with one final project! Create this tide pool craft, encouraging your child to include all the animals they’ve learned about this week in theirs. This is a great chance to review all that they’ve learned and see what they’ve retained! You could also make an oversized version and include the crafted animals that you’ve made throughout the week.

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Published by The Learn + Live Letter

The Learn + Live Letter is a play- and project-based homeschool curriculum for children ages 3-12.