A diving certification has the written and performance sections. He failed to retrieve his reg and panicked when his mask was flooded. Both aren't good, but its the panicking that's the problem. Panicking under water is a good way to fail. If you panic you make mistakes and making mistakes when your 60ft or more below can be fatal. Instructors watch applicants like hawks during the performance parts to ensure you have what it takes to dive safely. If you can't keep a level head then they wont pass you.