Teach your students about how the sun penetrates the ocean and affects plant and animal life there. The ocean has three zones: the sunlit, the twilight and the midnight zones. Bring a trash can to school and fill it with water in a shady spot on the playground. Let students take turns shining a flashlight into the can to see how light penetrates. Talk about how most ocean animals and fish live in the sunlight and twilight zones, and that no sunlight at all penetrates to the midnight zone.
If you live near an ocean, collect a bucket or two of seaweed for your students to experiment with. Provide microscopes and other equipment for observational purposes and teach them to collect data about the seaweed. Purchase some edible seaweed to bring in for your students to try and talk about how seaweed is a food staple in some cultures. Seaweed is also a habitat and food for ocean animals. Bring in a fish bowl with some strands of seaweed and a couple of fish so the students can see how the fish interact with the plant.
Many cities have aquariums that host ocean animals, fish and plants for your students to observe and study. Arrange a field trip to coincide with the end of your ocean unit. If a trip to the ocean is feasible, this is a chance for students to take a scientific look at a place they may have previously only played at. Bring the field to your class by inviting a university marine biology teacher, a local marine biologist or an aquarium employee to visit your students.
After studying coral, have your students design their own coral gardens. Make a stand by cutting a section of four cups from an egg carton. Turn it upside down and make an X-shaped cut in the center of the bottom of each cup. Provide your students with art supplies, such as pipe cleaners, tissue paper, construction paper, paints and small paper cups, along with pictures of coral to design their own crafty coral gardens. Glue crafted coral pieces to craft sticks, which students can insert into the cuts in the egg cartons.