This unit, one of a series designed to develop and foster an understanding of the marine environment, presents marine science activities for students in grades 7 and 8. The unit, focusing on life in the sea and the physical factors which influence that life, is divided into sections dealing with: (1) the theory of plate tectonics; (2) ocean floor topography; (3) the hydrologic cycle and weather; (4) adaptation and diversity; (5) marine food chains; (6) currents; (7) mining the ocean floor; (8) whaling; (9) offshore oil production; (10) boating and (11) the California gray whale population. Each section has a student text with related activities. Each student text is preceded by a teacher background section containing hints on how to use the section, additional information, and items requiring advanced planning. Each activity is preceded by a teacher background section providing additional information about the activity, including teaching hints and answer key for activities. Important vocabulary words/terms are listed in the teacher background sections; they are underlined in the student text. Activities are designed to enhance reading as well as investigational skills; several activities provide practice in mathematics skills. Although all activities can be modified to suit individual needs or be used "as is," it is strongly recommended that they be performed along with the readings/discussions found in student text material. (JM)