Learning to swim in a swimming pool might not prepare water competence sufficiently for different aquatic environments. The aim of this study was to assess the effectiveness of teaching children water safety knowledge and skills in open water environments (i.e., harbor, river, and surf). The aquatic knowledge and skills of 98 children (7-11 years old) were tested in a swimming pool before, immediately after, and three months after receiving a three-day intensive education program. At pre-test, typically fewer than 50% of children achieved a high level of water safety competence. After the program, competency in each of the six tasks assessed had increased with up to 80% of participants completing the tasks unassisted. Three-month retention of these skills was generally high (i.e., competency levels were either maintained or improved). A key challenge for future research will be to untangle the influences of maturation, order effects, and the open water education.