The website PreschoolRocks suggests having preschoolers make a wave bottle by filling a clean plastic bottle three-quarters full with water. Tint the water with a few drops of blue food coloring and add vegetable oil or baby oil to the bottle. Seal the bottle by placing a little bit of super glue on the inside of the lid and closing tightly. Roll the bottle slightly back and forth to show how the wave bottle mimics ocean waves. When preschoolers shake the bottle they will have their very own wave machine and will see how waves in the ocean work.
After teaching preschoolers about octopuses and their eight legs, allow them to create their own creature based on what they have learned. Have the children glue together two cup sections from the bottom of an egg carton to create a body; let this dry. Have them paint their octopus using the same colors that a real octopus would be–octopuses come in a variety of colors depending on their species. Colored pipe cleaners (eight of them) can serve as tentacles and can be glued on or poked through the carton. Students can also glue on googly eyes and draw on a mouth. After the craft is complete, explain that an octopus can change colors to blend in with its environment. Have children match their octopus to different parts of the classroom to see if theirs will be hard to distinguish from its surroundings.
PreschoolRocks also suggests having preschoolers make their own salt water. This simple science activity requires only salt, water and cups. Have kids dissolve salt in a cup of water; use about a teaspoon of salt per cup of water. Have students taste a small amount of the salt water if they want, then have a discussion about ocean water, what lives in it and what can happen if you consume too much of it.