Survival photo

A video of a big South American fish that caught a man off guard is quickly going viral.

The clip shows a group of fishermen struggling to subdue a huge arapaima, which are native to South America and one of the largest fish species in the world. Eventually, one of the men manages to coerce the head of the writhing arapaima into a sack then tries to lift it, with a bear-hug type move, but the fish bends back and whacks the man in the head—hard. You can hear the thud of skull-on-skull contact if you listen closely.

The man—knocked out cold—immediately goes limp and drops the arapaima. With the fish still flopping next to him, the other anglers pull their injured friend to safety, and the clip ends with the KO’d angler sitting upright, albeit dazed, with blood running down his face.