About 10 years ago a person I know and his son went on a try dive on holiday, Cyprus I think but certainly somewhere in that part of the Mediterranean. They were fitted with the gear, given about 5 minutes instruction standing chest deep in the sea then told to follow the instructor (or whoever he was). The father ran completely out of air at 13m and made a panicked ascent to the surface. He was very upset, even traumatized by the experience and has never attempted diving since. I also know of a group of teenagers with no previous dive experience and only a few minutes instruction being taken down to 15 to 20m on first dive, this was in Gibraltar.