The fundamental purposes of this study were to develop mastery tests in the cognitive and psychomotor domains for skin and scuba diving and to establish validity and reliability for the tests. A table of specifications was developed for each domain, and a pilot study refined the initial test batteries into their final form. In the main study, two-trial cognitive data were collected from 104 male and female college students enrolled in a skin and scuba diving course. Data were analyzed for test reliability and validity. Two skin diving and three scuba diving skills tests were administered to 98 subjects in two trials. One-way analysis of variance intraclass correlations were used to ascertain test-item reliability and validity. Both cognitive and psychomotor tests were found to be valid and reliable. Cutting scores were set for each test. Results showed the tests to be administratively feasible. (Author/MT)