Someone stole my petrol, tank and the outboard while I was in the pub at Menai Bridge. Funny how there was scheduled to be a boat jumble a week later....
A few years ago I had my boat laid up inside a locked shed at a boatyard on Hayling Island; keys supposedly held only by those with boats in the shed [deposit payable], and staff. I drained 5 litres out of my tank into a container and left it under the boat. Some swine stole it overnight. Not likely to be staff as it was pinched out-of-hours. I posted a notice on the door pointing out that it had not been discarded and inviting the thief to return it - he didn't.
It's not pleasant to think of a fellow yachtsman being a thief but I suppose it happens.
Not fuel, but I have just had two tins of paint pinched by a fellow boater....locked boat yard..which I had left under the boat. Outsiders not acceptable, but fellow boaters...scum!!