What is the PADI Junior Open Water Diver Course? The PADI Junior Open Water Diver Course is an entry level diver certification that is recognised world-wide. A PADI Junior Open Water Diver between the ages A PADI Junior Open Water Diver(12 to 14-year-old). Your certification automatically upgrades on your 15th birthday at which time you can apply to PADI for an adult certification card. The Jnr PADI Open Water Diver Course provides the knowledge and practical application for you to dive safely.