A bulk carrier was berthing, using a combination of ship’s and shorelines. The lines from shore were brought on board with the help of a long messenger line, which was placed on the warping drum to heave in.
Once the shoreline had been heaved onboard it was placed on the bitts. At one point, one of the deck crew wanted to slacken the messenger but unintentionally heaved the messenger line instead of slacking it. It parted and struck his legs violently.
He was not standing behind the controller...
https://www.marineinsight.com/case-studies/real-life-incident-messenger-line-snaps-injures-crew/