It takes at least four days to earn a scuba diving license through the Open Water Diver course. The process involves knowledge development, pool training, and open water dives. PADI eLearning allows self-paced learning, with open water dives spread over two days minimum. A wide time range accounts for individual learning speeds. An Open Water Diver Referral allows completing parts of the course locally and finishing dives later. Referral documents can be used globally within 12 months.