This manual contains instructions for laboratory exercises using marine organisms. For each exercise a problem is defined, materials are listed, possible ways to solve the problem are suggested, questions are asked to guide the student in interpreting data, and further reading is suggested. The exercises deal with the measurement of oxygen consumption in fish, population density, fertilization in the sea urchin, salinity tolerance, and food webs of shore organisms. This work was prepared under an ESEA Title III contract. (EB)