Choose a marine ecosystem and make a list of its physical features and the plants and animals that are typically found there. Consider characteristics such as temperature, light, salinity and type of land surface, as appropriate. Make note of animals and plants with special adaptations for this type of habitat.
Search through magazines and on the Internet for pictures of this ecosystem. Cut out or print useful pictures. Make special note of the color of the water and types of surfaces found in the ecosystem.
Create the ecosystem's background within the box. Use pictures cut from magazines or printed off the Internet; color or paint the inside of the box; or line it with colored paper to represent the colors of the water or sand and rock surfaces.
Cover the bottom of the inside of the box with glue and spread sand, rocks or potting soil along the bottom of the box to create sandy surfaces, rocky shores, or the silt-covered bottom of a mangrove swamp. Cover the potting soil with plastic wrap or cellophane to represent silt. Glue felt pieces to chunks of Styrofoam or paint rocks to represent coral and algae.
Place live or dried plant material that resembles the plant types found in the ecosystem, or use plastic plants, or pictures of plants.
Attach pictures, plastic toys or hand-drawn creatures to the model to complete the ecosystem. Tie swimming animals to fishing line and hang them from the top of the box. Attach other animals to craft sticks or toothpicks and push them through the bottom of the box. Glue pictures of animals to the sides of the box to create a three-dimensional effect.