I managed to do several, and preferred the SS dinghy. If using the multi-seater I always volunteered to be the lookout. Nice fresh air in the face rather than the smell as one after the other sitting inside proceeded to show what he had eaten for lunch. On one exercise we were doing the "parachute-dragging" bit, where the hapless victim was towed behind the launch. I made the excuse that, since I was a helicopter pilot, I wouldn't have to cope with the parachute. "Too right" said the instructor, and proceeded to push me off the back of the launch - lifejacket not inflated, and wearing a waistcoat type dinghy pack. After a few seconds (which seemed like minutes) descending to the bottom of Plymouth harbour, I got the jacket inflated and bobbed to the surface again.