Four lessons introduce elementary ecologists to salt marsh and sandy beach habitats. In the first lesson, they place shells and other materials in vinegar to determine if they contain calcium carbonate. In the second lesson, they read a mystery in which a blue crab has gone missing. The mystery is solved by the habitat clues that you provide. In the third lesson, learners make plankton models from playdough and experiment to see if different shapes float more readily. The final lesson prepares them for a field trip to the salt marsh.