Some of my more spectacular head first dives have been on and off pontoons!
Most notible wearing a drysuit, unfastened with the arms tied around my waist. One leg on boat the other on dry land.....with both parting at a rapid rate.
Luckily had the presence of mind to kick off the drysuit on my way down and re-surface.
Very wet, very cold (mid feb at the time) and not very happy once I'd realised I'd have to re-enter the water to collect my drysuit.......b*gger!