This is a descriptive study of a series of laboratory exercises on environmental microbiology carried out by students in a general microbiology course during eight of the twelve weeks of the semester. The revised laboratory component is predicated upon seawater and sediment samples collected by student pairs using marine sampling equipment on a field trip aboard a research vessel. Two longitudinal studies were performed: assay for antibiotic production from isolated actinomycetes and construction and observation of Winogradsky columns. Two additional experiments: culturing microalgae and water testing for coliforms also used the samples collected by the students. The advantages of long-term, challenging laboratory experiences actively involving the students in group process, self-direction, and scientific practices are discussed. Also considered are development of laboratory skills, scientific competencies, and students' self-confidence in carrying out such environmental investigations. Plans for future assessment of student learning are presented.