Went out on a friends powerboat to take photos with my 35mm and a bag full of lenses (this was back in the day). It was a glorious day and I went through rolls of film. Unfortunately in my excitement I forgot to double check the film. The Pentax had a nasty habit of kicking the film off the takeup spool during the first wind. I almost always doublechecked with the back of the camera open to see the film advance, the first few frames were leader anyhow......almost always, except for that day. When I had the film processed every roll was blank, never exposed they told me.