Can a Student Fail Open Water Scuba Certification? Does it really happen?
My limited experience in this was a summer of assisting with classes in Roatan, at one of the larger dive ops there, where they probably certified around 250 new divers while I was there. As far as I remember, only one failed to get her certification, and she was given the option to come back and continue the class to try to pass.
When I was certified many years ago at a dive shop in TX, there were two people in my class that I thought would be at danger of drowning if they went diving unsupervised in any sort of mildly challenging conditions, like a deep bottom, limited visibility, any current, etc...they both passed, although one of them knew enough to realize she was having a lot of trouble, and the instructor volunteered a few extra sessions with her to help with the skills. The other was clueless about his problems and got no extra help, but still got the C card. To this day I don't know how.
Most instructors, especially those working for dive shops whose business model is to sell gear to new divers, do not want to fail students in OW class. The shop doesn't want it either. I suspect many instructors, like the one that certified me, would spend extra time, and I mean an entire day, with students that are struggling rather than fail them.