The online booking form always asks divers for their certification

On a slow or dropped connection the booking form could forget that a dive needs a certification, and ask only for a date of birth. The diver would finish the form believing they were done, and you would find out at check-in.

It waits instead of guessing — if we cannot tell what the dive requires, the form asks the customer to hold a moment rather than letting them past with less.
Nobody was ever cleared to dive on this — check-in already refuses to board a diver whose details are missing, so this is about asking properly, not about who got on the boat.