Collect a variety of small seashells and ask the preschoolers to count them. The children can start counting by 1s, and gradually work toward counting by 10s and 5s as the school year progresses. Seashells are effective sorting tools, as well. Have the preschoolers sort a pile of seashells by size, color or shape, and then count how many of each there are. Extend the activity by asking which size, color or shape has the most and the least. Do the same counting and sorting activities with several sizes of colored construction paper circles, which can represent beach balls. Plastic ocean animal toys or colored construction paper fish cutouts in several sizes are also effective tools that preschoolers can use to count and sort.
Fill your sensory table with sand and add several pails in various sizes, as well as shovels. Encourage the preschoolers to fill the buckets with sand, asking them to tell you which buckets hold the most sand or how many scoops of sand each bucket holds. Ask the children to build sandcastles, giving instructions such as adding a small window or pressing three large shells into the side of the castle. These activities help preschoolers distinguish between sizes, and give a little extra practice with following directions. They're also entertaining, which is key for engagement in learning math concepts, according to the National Association for the Education of Young Children. Alternatively, fill the sensory table with water and add plastic ocean animals or boats. Ask the preschoolers to identify which animals or boats are the largest and which are the smallest.
Cut out several ocean-themed shapes in two or three colors. For example, cut out red starfish shapes, yellow seashell shapes and blue fish shapes. Lay several shapes on the floor in a pattern, such as yellow seashell, blue fish, red starfish, and ask preschoolers to take the rest of the shapes and finish the pattern. Reinforce pattern concepts even further by asking the preschoolers to start a pattern for a friend to finish. The ability to make and complete patterns helps prepare young children to understand more complex geometrical concepts as they get older. If your classroom has plastic pattern blocks, which usually come in triangle, square, rhombus and trapezoid shapes, set them out and ask preschoolers to make ocean-themed pictures with them. Ask the children to tell what shapes they're using as they work.
As a whole group, sequence seashells, plastic ocean animals or paper fish cutouts. For example, ask one child to place a shiny shell, octopus or red fish first in line. Then ask another child to put a round shell, starfish or green fish second in line. Continue ordering the ocean items, which will reinforce the concept of sequencing. You might also ask your students to wear their swimsuits or bring a beach towel to school, and sequence them according to the characteristics of their suits or towels. For example, ask all the children with red on their swim suits or towels to line up first and students with green on their suits or towels to line up second. Repeat the activity several times to help students get a firm grasp on the concept of first, second, third and so on.