Blue982
Contributor
To the OP, if you're being serious, was this a "discover scuba" course that you paid for or just a fun (illegal, but fun) dive with a "friend."
Small point: It's not illegal to dive uncertified. It's dumb and risky but entirely legal. Scuba diving, like ultralight flying and skydiving, self regulated before laws were put into place.
I have a friend who went diving in Mexico - no certification, no pool sessions, no instruction other than "don't hold your breath." I think what the OP describes is entirely plausible. When you consider how overweighted certified divers are, it wouldn't be a shock to me if the divemaster (probably in name only) accidentally dropped a weight belt and corked the OP. Also plausible, with somewhat sketchy dive operations, would be a simple equipment malfunction - stuck inflator.