Back.. way back when I was only 11, I was fishing in a local canal in the UK (the Bridgewater Canal, when the water was still ORANGE). Been catching fat carp most of the day and when this happened, i was trying to play another one.
Around the corner came a narrowboat loaded with coal. This canal was about 20ft wide and the narrowboat about 12ft wide and about 40ft long. These things can't stop very fast and keep smack in the middle of the canal by the water pressure between each side of the canal and the hull of the boat.
I tried as hard as i could, watching the boat approach. I started shouting, to no use as the capt is at the rear of the boat and its got a diesel pumping away.
Things happened and the carp went under the boat. Boat snagged my line, rod came out of my hand and started trailing behind the boat... carp in tow.
I must have run for about 2 miles after that boat trying to get the attention of the guy on the back. Finally just watched my rod and fish slowly dissapear.